Remove -Os from gyp C++ flags if it exists, since v8 uses -O3.

tools/gyp/v8.gyp

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 # modification, are permitted provided that the following conditions are
 # met:
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@@ skipping 63 matching lines @@
           'VCLinkerTool': {
             'LinkIncremental': '2',
           },
         },
       },
       'Release': {
         'conditions': [
           ['OS=="linux"', {
             'cflags!': [
               '-O2',
+              '-Os',
             ],
             'cflags': [
               '-fomit-frame-pointer',
               '-O3',

[Evan Martin, 2009/11/24 18:12:30]

Here, you can see that -O3 is introduced.  So the change I made only removes -Os
if it's present, since we want -O3 to always stick.

             ],
             'conditions': [
               [ 'gcc_version==44', {
                 'cflags': [
                   # Avoid gcc 4.4 strict aliasing issues in dtoa.c
                   '-fno-strict-aliasing',
                   # Avoid crashes with gcc 4.4 in the v8 test suite.
                   '-fno-tree-vrp',
                 ],
               }],
@@ skipping 473 matching lines @@
       ],
       'conditions': [
         [ 'OS=="win"', {
           # This could be gotten by not setting chromium_code, if that's OK.
           'defines': ['_CRT_SECURE_NO_WARNINGS'],
         }],
       ],
     },
   ],
 }