Allow <<< ATXXX >> code hooks in any part of the generated JS. NFC (#24042)

This also simplify the writing of the final module to use the common
`write_file` utility.

I think in the past the generated JS could be so large that python could
have trouble processing it but I think that dates back the asm.js days
when the generated JS conatains all the asm.js generated code. These
days the size of the JS clue is never proportional to the size of the
input C/C++ program like it was back then.

Author: sbc100

tools/emscripten.py

@@ -53,11 +53,6 @@
 ]
 
 
-def write_output_file(outfile, module):
-  for chunk in module:
-    outfile.write(chunk)
-
-
 def maybe_disable_filesystem(imports):
   """Disables filesystem if only a limited subset of syscalls is used.
 
@@ -412,13 +407,6 @@ def emscript(in_wasm, out_wasm, outfile_js, js_syms, finalize=True, base_metadat
 
   report_missing_exports(forwarded_json['librarySymbols'])
 
-  if settings.MINIMAL_RUNTIME:
-    # In MINIMAL_RUNTIME, atinit exists in the postamble part
-    post = apply_static_code_hooks(forwarded_json, post)
-  else:
-    # In regular runtime, atinits etc. exist in the preamble part
-    pre = apply_static_code_hooks(forwarded_json, pre)
-
   asm_const_pairs = ['%s: %s' % (key, value) for key, value in asm_consts]
   if asm_const_pairs or settings.MAIN_MODULE:
     pre += 'var ASM_CONSTS = {\n  ' + ',  \n '.join(asm_const_pairs) + '\n};\n'
@@ -440,20 +428,18 @@ def emscript(in_wasm, out_wasm, outfile_js, js_syms, finalize=True, base_metadat
     function_exports['asyncify_start_rewind'] = webassembly.FuncType([webassembly.Type.I32], [])
     function_exports['asyncify_stop_rewind'] = webassembly.FuncType([], [])
 
-  with open(outfile_js, 'w', encoding='utf-8') as out:
-    out.write(pre)
-    pre = None
-
-    receiving = create_receiving(function_exports)
-    if settings.WASM_ESM_INTEGRATION:
-      sending = create_sending(metadata, forwarded_json['librarySymbols'])
-      module = [sending, receiving]
-    else:
-      module = create_module(receiving, metadata, global_exports, forwarded_json['librarySymbols'])
-    write_output_file(out, module)
+  parts = [pre]
+  receiving = create_receiving(function_exports)
+  if settings.WASM_ESM_INTEGRATION:
+    sending = create_sending(metadata, forwarded_json['librarySymbols'])
+    parts += [sending, receiving]
+  else:
+    parts += create_module(receiving, metadata, global_exports, forwarded_json['librarySymbols'])
+  parts.append(post)
 
-    out.write(post)
-    module = None
+  full_js_module = ''.join(parts)
+  full_js_module = apply_static_code_hooks(forwarded_json, full_js_module)
+  utils.write_file(outfile_js, full_js_module)
 
   metadata.library_definitions = forwarded_json['libraryDefinitions']
   return metadata