Set cc_flags for cmake build on Mac

gyp/common_conditions.gypi

Index: gyp/common_conditions.gypi
diff --git a/gyp/common_conditions.gypi b/gyp/common_conditions.gypi
index 8221c94680a645a68b91927d83276065b042fb69..8d1e2655b6c7a0406692d5b3d00c501094fa29ee 100644
--- a/gyp/common_conditions.gypi
+++ b/gyp/common_conditions.gypi
@@ -519,6 +519,7 @@
               'LIBRARY_SEARCH_PATHS': [ '/usr/lib -fsanitize=<(skia_sanitizer)'],
             }],
           ],
+          # Keep these in sync with cflags_cc below
           'CLANG_CXX_LIBRARY':                         'libc++',
           'CLANG_CXX_LANGUAGE_STANDARD':               'c++11',
           'GCC_ENABLE_CPP_EXCEPTIONS':                 'NO',   # -fno-exceptions
@@ -539,6 +540,21 @@
             '-Wno-unused-parameter',
           ],
         },
+        # Keep these in sync with xcode settings above
+        'cflags_cc': [
+          '-std=c++11',
+          '-fno-rtti',
+          '-fno-threadsafe-statics',
+          '-mssse3',
+          '-fvisibility=hidden',
+          '-fvisibility-inlines-hidden',
+          '-Wall',
+          '-Wextra',
+          '-Winit-self',
+          '-Wpointer-arith',
+          '-Wsign-compare',
+          '-Wno-unused-parameter',
+        ],
       },
     ],