gyp: build with gnu++0x for the sake of new v8

The new v8 doesn't build on non gnu++0x, set it to a proper value for
all systems.

common.gypi

@@ -173,7 +173,7 @@
       }],
       [ 'OS in "linux freebsd openbsd solaris android"', {
         'cflags': [ '-Wall', '-Wextra', '-Wno-unused-parameter', ],
-        'cflags_cc': [ '-fno-rtti', '-fno-exceptions' ],
+        'cflags_cc': [ '-fno-rtti', '-fno-exceptions', '-std=gnu++0x' ],
         'ldflags': [ '-rdynamic' ],
         'target_conditions': [
           ['_type=="static_library"', {
@@ -237,6 +237,12 @@
           ['target_arch=="x64"', {
             'xcode_settings': {'ARCHS': ['x86_64']},
           }],
+          ['clang==1', {
+            'xcode_settings': {
+              'GCC_VERSION': 'com.apple.compilers.llvm.clang.1_0',
+              'CLANG_CXX_LANGUAGE_STANDARD': 'gnu++0x',  # -std=gnu++0x
+            },
+          }],
         ],
       }],
       ['OS=="freebsd" and node_use_dtrace=="true"', {