Enable building Skia for iOS with bazel.

tools/flags/SkCommandLineFlags.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCommandLineFlags.h"
 #include "SkTDArray.h"
 #include "SkTSort.h"
 
 #include <stdlib.h>
 
-#if defined(GOOGLE3) && defined(SK_BUILD_FOR_ANDROID)
-    // I don't know why, but this is defined by //base only for Android.
+#if defined(GOOGLE3) && (defined(SK_BUILD_FOR_ANDROID) || defined(SK_BUILD_FOR_IOS))
+    // I don't know why, but this is defined by //base only for non-Linux.
     DECLARE_bool(undefok)
 #else
     DEFINE_bool(undefok, false, "Silently ignore unknown flags instead of crashing.");
 #endif
 
 template <typename T> static void ignore_result(const T&) {}
 
 bool SkFlagInfo::CreateStringFlag(const char* name, const char* shortName,
                                   SkCommandLineFlags::StringArray* pStrings,
                                   const char* defaultValue, const char* helpString) {
@@ skipping 356 matching lines @@
 }
 
 }  // namespace
 
 bool SkCommandLineFlags::ShouldSkip(const SkTDArray<const char*>& strings, const char* name) {
     return ShouldSkipImpl(strings, name);
 }
 bool SkCommandLineFlags::ShouldSkip(const StringArray& strings, const char* name) {
     return ShouldSkipImpl(strings, name);
 }