Remove -mfpmath=sse for clang, which does it automatically and sometimes is annoyed by it.

gyp/common_conditions.gypi

 # conditions used in both common.gypi and skia.gyp in chromium
 #
 {
   'defines': [
     'SK_ALLOW_STATIC_GLOBAL_INITIALIZERS=<(skia_static_initializers)',
     'SK_SUPPORT_GPU=<(skia_gpu)',
     'SK_SUPPORT_OPENCL=<(skia_opencl)',
     'SK_FORCE_DISTANCEFIELD_FONTS=<(skia_force_distancefield_fonts)',
   ],
   'conditions' : [
@@ skipping 417 matching lines @@
                   }],
                 ],
               }],
             ],
           }],
           [ 'skia_clang_build', {
             'cflags': [
               # Extra warnings we like but that only Clang knows about.
               '-Wstring-conversion',
             ],
+            'cflags!': [
+                '-mfpmath=sse',  # Clang doesn't need to be told this, and sometimes gets confused.
+            ],
           }],
           [ 'skia_keep_frame_pointer', {
             'cflags': [ '-fno-omit-frame-pointer' ],
           }],
         ],
       },
     ],
 
     [ 'skia_os == "mac"',
       {
@@ skipping 203 matching lines @@
         'SK_BUILD_JSON_WRITER',
       ]
     }],
 
   ], # end 'conditions'
   # The Xcode SYMROOT must be at the root. See build/common.gypi in chromium for more details
   'xcode_settings': {
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }