Fix argv passing in PROXY_TO_PTHREAD mode

This was broken in #17153 but we didn't have any tests.  The fix is
to export `main` even though we don't technically need to.  We could
add a little complexity to allow metadce to remove it, but I'm not
sure its worth it.

Fixes: #17338

Author: sbc100

emcc.py

@@ -1747,9 +1747,7 @@ def phase_linker_setup(options, state, newargs, user_settings):
         settings.EXPECT_MAIN = 0
     else:
       assert not settings.EXPORTED_FUNCTIONS
-      # With PROXY_TO_PTHREAD we don't export `main` at all but instead `_emscripten_proxy_main`.
-      if not settings.PROXY_TO_PTHREAD:
-        settings.EXPORTED_FUNCTIONS = ['_main']
+      settings.EXPORTED_FUNCTIONS = ['_main']
 
   if settings.STANDALONE_WASM:
     # In STANDALONE_WASM mode we either build a command or a reactor.

tests/core/test_hello_argc.c

@@ -6,7 +6,13 @@
  */
 
 #include <stdio.h>
+
 int main(int argc, char** argv) {
   printf("hello, world! %d\n", argc);
+  // Skip arg 0 because it will be an absolute path that varies between
+  // machines.
+  for (int i = 1; i < argc; i++) {
+    printf("%d: %s\n", i, argv[i]);
+  }
   return 0;
 }

tests/core/test_hello_argc.out

@@ -1 +1,3 @@
-hello, world! 1
+hello, world! 3
+1: hello
+2: world

tests/other/metadce/test_metadce_minimal_pthreads.exports

@@ -2,6 +2,7 @@ A
 B
 C
 D
+E
 o
 p
 q

tests/other/metadce/test_metadce_minimal_pthreads.funcs

@@ -46,6 +46,7 @@ $emscripten_stack_set_limits
 $get_tasks_for_thread
 $init_file_lock
 $init_mparams
+$main
 $memset
 $pthread_attr_destroy
 $sbrk

tests/other/metadce/test_metadce_minimal_pthreads.jssize

@@ -1 +1 @@
-15917
+15983

tests/other/metadce/test_metadce_minimal_pthreads.size

@@ -1 +1 @@
-18289
+18299

tests/test_core.py

@@ -459,7 +459,13 @@ def test_wasm_synchronous_compilation(self):
 
   @also_with_standalone_wasm()
   def test_hello_argc(self):
-    self.do_core_test('test_hello_argc.c')
+    self.do_core_test('test_hello_argc.c', args=['hello', 'world'])
+
+  @node_pthreads
+  def test_hello_argc_pthreads(self):
+    self.set_setting('PROXY_TO_PTHREAD')
+    self.set_setting('EXIT_RUNTIME')
+    self.do_core_test('test_hello_argc.c', args=['hello', 'world'])
 
   @also_with_wasmfs
   def test_intvars(self):