Set -fobjc-call-cxx-cdtors in .m[m] files in the GN build.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium 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/android/config.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 
 # compiler ---------------------------------------------------------------------
@@ skipping 53 matching lines @@
     # These flags are shared between the C compiler and linker.
     common_mac_flags = []
 
     # CPU architecture.
     if (cpu_arch == "x64") {
       common_mac_flags += [ "-arch x86_64" ]
     } else if (cpu_arch == "x86") {
       common_mac_flags += [ "-arch i386" ]
     }
 
-    cflags += common_mac_flags + [
-      # Without this, the constructors and destructors of a C++ object inside
-      # an Objective C struct won't be called, which is very bad.
-      "-fobjc-call-cxx-cdtors",
-    ]
+    cflags += common_mac_flags
+
+    # Without this, the constructors and destructors of a C++ object inside
+    # an Objective C struct won't be called, which is very bad.
+    cflags_objcc = [ "-fobjc-call-cxx-cdtors", ]
 
     cflags_c += [ "-std=c99" ]
     cflags_cc += [ "-std=gnu++11" ]
 
     ldflags += common_mac_flags + [
       "-L.",
 
       # TODO(brettW) I don't understand these options.
       "-Wl,-rpath,@loader_path/.",
       "-Wl,-rpath,@loader_path/../../..",
@@ skipping 564 matching lines @@
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }