gn/clang: Only pass -Wno-reserved-user-defined-literal on Linux and Android.

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")
 import("//build/config/chrome_build.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
@@ skipping 941 matching lines @@
 
     # Clang considers the `register` keyword as deprecated, but e.g.
     # code generated by flex (used in angle) contains that keyword.
     # http://crbug.com/255186
     "-Wno-deprecated-register",
 
     # TODO(thakis): This used to be implied by -Wno-unused-function,
     # which we no longer use. Check if it makes sense to remove
     # this as well. http://crbug.com/316352
     "-Wno-unneeded-internal-declaration",
+  ]
 
-    # TODO(thakis): Remove, http://crbug.com/263960
-    "-Wno-reserved-user-defined-literal",
-  ]
+  if (is_posix && !is_mac && !is_ios) {
+    default_warning_flags += [
+      # TODO(thakis): Remove, http://crbug.com/263960
+      "-Wno-reserved-user-defined-literal",
+    ]
+  }
 
   # NaCl's Clang compiler and Chrome's hermetic Clang compiler will almost
   # always have different versions. Certain flags may not be recognized by
   # one version or the other.
   if (!is_nacl) {
     # Flags NaCl does not recognize.
     default_warning_flags += [
       # TODO(hans): Get this cleaned up, http://crbug.com/428099
       "-Wno-inconsistent-missing-override",
 
@@ skipping 355 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }