[gn] Enable stricter build flags

src/wasm/wasm-module-builder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/signature.h"
 
 #include "src/handles.h"
 #include "src/objects-inl.h"
 #include "src/v8.h"
 #include "src/zone/zone-containers.h"
@@ skipping 349 matching lines @@
     FixupSection(buffer, start);
   }
 
   // == Emit function signatures ===============================================
   bool has_names = false;
   if (functions_.size() > 0) {
     size_t start = EmitSection(kFunctionSectionCode, buffer);
     buffer.write_size(functions_.size());
     for (auto function : functions_) {
       function->WriteSignature(buffer);
-      exports += function->exported_names_.size();
+      exports += static_cast<uint32_t>(function->exported_names_.size());
       if (function->name_.size() > 0) has_names = true;
     }
     FixupSection(buffer, start);
   }
 
   // == emit function table ====================================================
   if (indirect_functions_.size() > 0) {
     size_t start = EmitSection(kTableSectionCode, buffer);
     buffer.write_u8(1);  // table count
     buffer.write_u8(kWasmAnyFunctionTypeForm);
@@ skipping 176 matching lines @@
   // Emit the offset table per function.
   for (auto function : functions_) {
     function->WriteAsmWasmOffsetTable(buffer);
   }
   // Append a 0 to indicate that this is an encoded table.
   buffer.write_u8(0);
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8