Build specialized version of glslang

Bug: angleproject:4763
Change-Id: Ibb98c872a1283b9d6acde958a7c5212cf79e72df
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2281618
Reviewed-by: Jamie Madill <[email protected]>
Reviewed-by: Tobin Ehlis <[email protected]>
Commit-Queue: Shahbaz Youssefi <[email protected]>

Author: ShabbyX

BUILD.gn

@@ -578,7 +578,7 @@ if (angle_enable_vulkan || angle_enable_metal) {
     deps = [
       ":libANGLE_headers",
       "${angle_glslang_dir}:glslang_default_resource_limits_sources",
-      "${angle_glslang_dir}:glslang_sources",
+      "${angle_glslang_dir}:glslang_lib_sources",
       "${angle_spirv_headers_dir}:spv_headers",
       "${angle_spirv_tools_dir}:spvtools_headers",
     ]

build_overrides/glslang.gni

@@ -5,5 +5,6 @@
 # Paths to glslang dependencies in ANGLE
 glslang_spirv_tools_dir = "//third_party/spirv-tools/src"
 
-# Temporary to unblock glslang roll.  Will change to true afterwards.
-glslang_angle = false
+# Reduce glslang's features to what the Vulkan backend of ANGLE uses. This both speeds up glslang's
+# initialization and reduces binary footprint.
+glslang_angle = true

scripts/export_targets.py

@@ -218,6 +218,7 @@ def pre(k):
 }
 
 IGNORED_DIRECTORIES = {
+    '//third_party/glslang',
     '//third_party/SwiftShader',
     '//third_party/vulkan-headers',
     '//third_party/vulkan-loader',

src/tests/BUILD.gn

@@ -276,7 +276,7 @@ if (is_win || is_linux || is_android || is_mac) {
     if (angle_enable_vulkan && !is_mac) {
       sources += angle_white_box_perf_tests_vulkan_sources
       deps += [
-        "$angle_glslang_dir:glslang_sources",
+        "$angle_glslang_dir:glslang_lib_sources",
         "$angle_root/src/common/vulkan:angle_vulkan_entry_points",
       ]
     }
@@ -1310,7 +1310,7 @@ if (build_angle_deqp_tests && !is_fuchsia) {
     public_deps = [
       ":angle_deqp_framework_egl",
       ":angle_deqp_glshared",
-      "${angle_glslang_dir}:glslang_sources",
+      "${angle_glslang_dir}:glslang_lib_sources",
       "${angle_spirv_tools_dir}:spvtools_val",
     ]
     public_configs = [ ":angle_deqp_khr_common_config" ]