Use MACOSX_DEPLOYMENT_TARGET instead of SDKROOT.

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_DISTANCEFIELD_FONTS=<(skia_distancefield_fonts)',
   ],
   'conditions' : [
@@ skipping 282 matching lines @@
           }],
           [ 'skia_keep_frame_pointer', {
             'cflags': [ '-fno-omit-frame-pointer' ],
           }],
         ],
       },
     ],
 
     [ 'skia_os == "mac"',
       {
-        'variables': {
-          'mac_sdk%': '<!(python <(DEPTH)/tools/find_mac_sdk.py 10.6)',
-        },
         'defines': [
           'SK_BUILD_FOR_MAC',
         ],
         'conditions' : [
           [ 'skia_arch_width == 64', {
             'xcode_settings': {
               'ARCHS': ['x86_64'],
             },
           }],
           [ 'skia_arch_width == 32', {
             'xcode_settings': {
               'ARCHS': ['i386'],
             },
           }],
           [ 'skia_warnings_as_errors', {
             'xcode_settings': {
               'OTHER_CPLUSPLUSFLAGS': [
                 '-Werror',
                 '-Wall',
                 '-Wextra',
                 '-Wno-unused-parameter',
+                '-Wno-uninitialized',  # Disabled because we think GCC 4.2 is bad at this.
               ],
             },
           }],
-# This old compiler is really bad at figuring out when things are uninitialized, so ignore it.
-          [ '<(mac_sdk)==10.6', {
-            'xcode_settings': {
-              'OTHER_CPLUSPLUSFLAGS': [
-                '-Wno-uninitialized',
-              ],
-            },
-          }],
         ],
         'configurations': {
           'Coverage': {
             'xcode_settings': {
                'GCC_OPTIMIZATION_LEVEL': '0',
                'GCC_GENERATE_TEST_COVERAGE_FILES': 'YES',
                'GCC_INSTRUMENT_PROGRAM_FLOW_ARCS' : 'YES',
             },
           },
           'Debug': {
             'xcode_settings': {
               'GCC_OPTIMIZATION_LEVEL': '0',
             },
           },
           'Release': {
             'xcode_settings': {
               'GCC_OPTIMIZATION_LEVEL': '<(skia_release_optimization_level)',
             },
             'defines': [ 'NDEBUG' ],
           },
         },
         'xcode_settings': {
           'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO',
-          'conditions': [
-            [ 'skia_osx_sdkroot==""', {
-              'SDKROOT': 'macosx<(mac_sdk)',  # -isysroot
-            }, {
-              'SDKROOT': '<(skia_osx_sdkroot)',  # -isysroot
-            }],
-           ],
+          'MACOSX_DEPLOYMENT_TARGET': '10.6', # -mmacos-version-min, passed in environment to ld.
 # trying to get this to work, but it needs clang I think...
 #          'WARNING_CFLAGS': '-Wexit-time-destructors',
           'CLANG_WARN_CXX0X_EXTENSIONS': 'NO',
           'GCC_WARN_64_TO_32_BIT_CONVERSION': 'YES',
           'GCC_WARN_ABOUT_DEPRECATED_FUNCTIONS': 'YES',
           'GCC_WARN_ABOUT_INVALID_OFFSETOF_MACRO': 'YES',
           'GCC_WARN_ABOUT_MISSING_NEWLINE': 'YES',
           'GCC_WARN_ABOUT_MISSING_PROTOTYPES': 'YES',
           'GCC_WARN_ABOUT_POINTER_SIGNEDNESS': 'YES',
           'GCC_WARN_ABOUT_RETURN_TYPE': 'YES',
@@ skipping 106 matching lines @@
       'defines': [
         'SK_USE_POSIX_THREADS',
       ],
     }],
   ], # end 'conditions'
   # The Xcode SYMROOT must be at the root. See build/common.gypi in chromium for more details
   'xcode_settings': {
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }