Revert "[Fuchsia] Remove the legacy gn build rules for fuchsia"

This reverts commit 094202b.

Reason for revert: Break flutter, this change should happen after
flutter being migrated to the same gn-sdk.

Original change's description:
> [Fuchsia] Remove the legacy gn build rules for fuchsia
>
> The updated test-scripts contains https://crrev.com/c/5341620 which
> allows to generate fidl apis with an env var controlled location
> rather than a hard-coded one. So the existing fuchsia gn build rules
> in dart/sdk become obsolete and can be fully removed in favor of the
> one in //third_party/fuchsia/gn-sdk/.
>
> Meanwhile the gn-sdk has been updated with
> https://crrev.com/c/5325282 to use api-level version'ed idk but not
> the ones in arch/.
>
> Cq-Include-Trybots: luci.dart.try:vm-fuchsia-release-arm64-try,vm-fuchsia-release-x64-try
> Tested: ^^^^^
> Bug: 40935282
> Change-Id: I2ce958e6db1ff8221beef7b7ff953c32bb4525ba
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/355283
> Reviewed-by: Ryan Macnak <[email protected]>
> Reviewed-by: Alexander Thomas <[email protected]>
> Commit-Queue: Zijie He <[email protected]>

Bug: 40935282
Change-Id: I7c455d1d362210523671c97d99ef018ede1743f4
Cq-Include-Trybots: luci.dart.try:vm-fuchsia-release-arm64-try,vm-fuchsia-release-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/356307
Bot-Commit: Rubber Stamper <[email protected]>
Auto-Submit: Zijie He <[email protected]>
Reviewed-by: Derek Xu <[email protected]>
Commit-Queue: Zijie He <[email protected]>

Author: zijiehe-google-com

DEPS

@@ -700,7 +700,7 @@ Var("dart_root") + "/third_party/pkg/tar":
     "packages": [
       {
       "package": "chromium/fuchsia/test-scripts",
-      "version": "EAdD2YcYwVrhF2q_zR6xUvPkcKlPb1tJyM_6_oOc84kC",
+      "version": "version:2@49064713a73ae92d8c28164938b97869afd336aa",
       }
     ],
     "condition": 'download_fuchsia_deps',
@@ -711,7 +711,7 @@ Var("dart_root") + "/third_party/pkg/tar":
     "packages": [
       {
       "package": "chromium/fuchsia/gn-sdk",
-      "version": "RgErspyYHapUO2SpcW-vo2p8yaRUMUrq0eWjRVPfQjoC",
+      "version": "version:2@7f1f23fce153ca079a77492d9d47d803d60b774e",
       }
     ],
     "condition": 'download_fuchsia_deps',
@@ -836,16 +836,6 @@ hooks = [
         Var('emsdk_ver')],
     'condition': 'download_emscripten'
   },
-  {
-    'name': 'Erase arch/ from fuchsia sdk',
-    'pattern': '.',
-    'action': [
-      'rm',
-      '-rf',
-      'sdk/third_party/fuchsia/sdk/linux/arch',
-    ],
-    'condition': 'download_fuchsia_deps'
-  },
   {
     'name': 'Download Fuchsia system images',
     'pattern': '.',
@@ -857,14 +847,4 @@ hooks = [
     ],
     'condition': 'download_fuchsia_deps'
   },
-  {
-    'name': 'Generate Fuchsia GN build rules',
-    'pattern': '.',
-    'action': [
-      'python3',
-      'sdk/build/fuchsia/with_envs.py',
-      'sdk/third_party/fuchsia/test_scripts/gen_build_defs.py',
-    ],
-    'condition': 'download_fuchsia_deps'
-  },
 ]

build/config/BUILDCONFIG.gn

@@ -257,7 +257,9 @@ if (is_win) {
     "//build/config/win:winver",
   ]
   if (is_clang) {
-    _native_compiler_configs += [ "//build/config/win:relative_paths" ]
+    _native_compiler_configs += [
+      "//build/config/win:relative_paths",
+    ]
   }
 }
 if (is_posix) {
@@ -268,8 +270,8 @@ if (is_posix) {
 }
 if (is_fuchsia) {
   _native_compiler_configs += [
-    "//third_party/fuchsia/gn-sdk/src/config:compiler",
-    "//third_party/fuchsia/gn-sdk/src/config:runtime_library",
+    "//build/config/fuchsia:compiler",
+    "//build/config/fuchsia:runtime_library",
   ]
 }
 
@@ -448,8 +450,8 @@ foreach(_target_type,
         }
         if (is_fuchsia) {
           deps += [
+            "//build/config/fuchsia:runtime_library_group",
             "//build/fuchsia/config/clang:c++-runtime-deps",
-            "//third_party/fuchsia/gn-sdk/src/config:runtime_library_group",
           ]
         }
       }

build/config/fuchsia/BUILD.gn

@@ -0,0 +1,89 @@
+# Copyright 2019 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/fuchsia/gn_configs.gni")
+
+config("compiler") {
+  sdk_version = "${fuchsia_sdk_id}"
+  defines = [
+    # To force full builds after SDK updates in case of ABI changes.
+    "FUCHSIA_SDK_VERSION=$sdk_version",
+  ]
+  cflags = []
+  ldflags = []
+  if (current_cpu == "arm64") {
+    cflags += [ "--target=aarch64-fuchsia" ]
+  } else if (current_cpu == "x64") {
+    cflags += [ "--target=x86_64-fuchsia" ]
+  } else {
+    assert(false, "Unsupported architecture")
+  }
+
+  # Pass the target API level to the compiler if specified.
+  if (fuchsia_target_api_level != -1) {
+    cflags += [ "-ffuchsia-api-level=${fuchsia_target_api_level}" ]
+  }
+
+  # Add libfdio by default. This may change in future versions
+  # in order to move away from POSIX applications and towards
+  # the Fuchsia programming model.
+  ldflags += [
+    # We always want fdio or else e.g. stdio wouldn't be initialized if fdio
+    # happens to not be directly referenced. The common POSIX-y compiler setup
+    # uses -Wl,--as-needed which drops it if it's simply "-lfdio" from a libs
+    # setting. Disable --as-needed, add fdio, and then set back to --as-needed.
+    "-Wl,--no-as-needed",
+    "-lfdio",
+    "-Wl,--as-needed",
+  ]
+
+  lib_dirs = [ "${fuchsia_sdk}/arch/${current_cpu}/lib" ]
+
+  libs = [ "zircon" ]
+
+  ldflags += cflags
+  asmflags = cflags
+}
+
+# This should be applied to all targets.
+config("runtime_library") {
+  asmflags = []
+  cflags = []
+  cflags_c = []
+  cflags_cc = []
+  cflags_objc = []
+  cflags_objcc = []
+  defines = []
+  ldflags = []
+
+  sysroot = "${fuchsia_sdk}/arch/$current_cpu/sysroot"
+
+  # Pass the sysroot to all C compiler variants, the assembler, and linker.
+  cflags = [ "--sysroot=" + rebase_path(sysroot, root_build_dir) ]
+  ldflags = cflags
+  asmflags = cflags
+}
+
+# Copy the loader to place it at the expected path in the final package.
+copy("sysroot_dist_libs") {
+  sources = [ "${fuchsia_sdk}/arch/${target_cpu}/sysroot/dist/lib/ld.so.1" ]
+  outputs = [ "${root_out_dir}/lib/{{source_file_part}}" ]
+}
+
+# This adds the runtime deps for //build/config/compiler:runtime_library
+# as that is a config target and thus cannot include data_deps.
+group("runtime_library_group") {
+  data_deps = [
+    ":sysroot_dist_libs",
+
+    # This is used directly from //build/config/fuchsia:compiler and thus
+    # also needs to be included by default.
+    # "${fuchsia_sdk}/pkg/fdio",
+  ]
+}
+
+config("sdk_lib_dirs_config") {
+  visibility = [ "${fuchsia_sdk}/*" ]
+  lib_dirs = [ "arch/${target_cpu}/lib" ]
+}

build/fuchsia/fidl/BUILD.gn

@@ -0,0 +1,11 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+assert(is_fuchsia)
+import("//build/fuchsia/sdk.gni")
+
+fuchsia_sdk("fidl") {
+  meta = "$fuchsia_sdk_path/meta/manifest.json"
+  enabled_parts = [ "fidl_library" ]
+}

build/fuchsia/fidl_gen_cpp.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+#
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+""" Generate C/C++ headers and source files from the set of FIDL files specified
+in the meta.json manifest.
+"""
+
+
+import argparse
+import collections
+import json
+import os
+import subprocess
+import sys
+
+def GetFIDLFilesRecursive(libraries, sdk_base, path):
+  with open(path) as json_file:
+    parsed = json.load(json_file)
+    result = []
+    deps =  parsed['deps']
+    for dep in deps:
+      dep_meta_json = os.path.abspath('%s/fidl/%s/meta.json' % (sdk_base, dep))
+      GetFIDLFilesRecursive(libraries, sdk_base, dep_meta_json)
+    libraries[parsed['name']] = result + parsed['sources']
+
+def GetFIDLFilesByLibraryName(sdk_base, root):
+  libraries = collections.OrderedDict()
+  GetFIDLFilesRecursive(libraries, sdk_base, root)
+  return libraries
+
+def main():
+  parser = argparse.ArgumentParser();
+
+  parser.add_argument('--fidlc-bin', dest='fidlc_bin', action='store', required=True)
+  parser.add_argument('--fidlgen-bin', dest='fidlgen_bin', action='append', required=False)
+
+  parser.add_argument('--sdk-base', dest='sdk_base', action='store', required=True)
+  parser.add_argument('--root', dest='root', action='store', required=True)
+  parser.add_argument('--json', dest='json', action='store', required=True)
+  parser.add_argument('--fidlgen-output-root', dest='fidlgen_output_root', action='store', required=False)
+  parser.add_argument('--target-api-level', dest='target_api_level', action='store', required=False)
+
+  args = parser.parse_args()
+
+  assert os.path.exists(args.fidlc_bin)
+
+  fidl_files_by_name = GetFIDLFilesByLibraryName(args.sdk_base, args.root)
+
+  fidlc_command = [
+    args.fidlc_bin,
+    '--json',
+    args.json
+  ]
+
+  if args.target_api_level:
+    fidlc_command += [
+      '--available',
+      'fuchsia:{api_level}'.format(api_level=args.target_api_level),
+    ]
+
+  # Create an iterator that works on both python3 and python2
+  try:
+    fidl_files_by_name_iter = list(fidl_files_by_name.items())
+  except AttributeError:
+    fidl_files_by_name_iter = iter(fidl_files_by_name.items())
+
+  for _, fidl_files in fidl_files_by_name_iter:
+    fidlc_command.append('--files')
+    for fidl_file in fidl_files:
+      fidl_abspath = os.path.abspath('%s/%s' % (args.sdk_base, fidl_file))
+      fidlc_command.append(fidl_abspath)
+
+  subprocess.check_call(fidlc_command)
+
+  if args.fidlgen_output_root:
+    assert os.path.exists(args.json)
+    for fidlgen_bin in args.fidlgen_bin:
+      assert os.path.exists(fidlgen_bin)
+
+      fidlgen_command = [
+        fidlgen_bin,
+        '-json',
+        args.json,
+        '-root',
+        args.fidlgen_output_root
+      ]
+
+      subprocess.check_call(fidlgen_command)
+  else:
+    # --fidlgen-bin and --fidlgen-output-root should be passed in together.
+    assert not args.fidlgen_bin
+
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(main())

build/fuchsia/pkg/BUILD.gn

@@ -0,0 +1,14 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+assert(is_fuchsia)
+import("//build/fuchsia/sdk.gni")
+
+fuchsia_sdk("pkg") {
+  meta = "$fuchsia_sdk_path/meta/manifest.json"
+  enabled_parts = [
+    "cc_source_library",
+    "cc_prebuilt_library",
+  ]
+}