Enable override keyword for GCC versions >= 4.7

include/core/SkPostConfig.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPostConfig_DEFINED
 #define SkPostConfig_DEFINED
 
@@ skipping 284 matching lines @@
      // Clang defaults to C++03 and warns about using override. Squelch that. Intentionally no
      // push/pop here so all users of SK_OVERRIDE ignore the warning too. This is like passing
      // -Wno-c++11-extensions, except that GCC won't die (because it won't see this pragma).
 #    pragma clang diagnostic ignored "-Wc++11-extensions"
 #
 #    if __has_feature(cxx_override_control)
 #      define SK_OVERRIDE override
 #    elif defined(__has_extension) && __has_extension(cxx_override_control)
 #      define SK_OVERRIDE override
 #    endif
+   // if GCC >= 4.7
+#  elif defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
+#    define SK_OVERRIDE override
 #  endif
 #  ifndef SK_OVERRIDE
 #    define SK_OVERRIDE
 #  endif
 #endif
 
 //////////////////////////////////////////////////////////////////////
 
 #if !defined(SK_UNUSED)
 #  define SK_UNUSED SK_ATTRIBUTE(unused)
@@ skipping 76 matching lines @@
 
 #if defined(SK_GAMMA_EXPONENT) && defined(SK_GAMMA_SRGB)
 #  error "cannot define both SK_GAMMA_EXPONENT and SK_GAMMA_SRGB"
 #elif defined(SK_GAMMA_SRGB)
 #  define SK_GAMMA_EXPONENT (0.0f)
 #elif !defined(SK_GAMMA_EXPONENT)
 #  define SK_GAMMA_EXPONENT (2.2f)
 #endif
 
 #endif // SkPostConfig_DEFINED