Fix Mac Breakpad host tools to build in Linux cross-compile

src/common/common.gyp

 # Copyright 2014 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 102 matching lines @@
         'linux/safe_readlink.cc',
         'linux/safe_readlink.h',
         'linux/synth_elf.cc',
         'linux/synth_elf.h',
         'mac/arch_utilities.cc',
         'mac/arch_utilities.h',
         'mac/bootstrap_compat.cc',
         'mac/bootstrap_compat.h',
         'mac/byteswap.h',
         'mac/dump_syms.h',
-        'mac/dump_syms.mm',
+        'mac/dump_syms.cc',
         'mac/file_id.cc',
         'mac/file_id.h',
         'mac/GTMDefines.h',
         'mac/GTMLogger.h',
         'mac/GTMLogger.m',
         'mac/HTTPMultipartUpload.h',
         'mac/HTTPMultipartUpload.m',
         'mac/MachIPC.h',
         'mac/MachIPC.mm',
         'mac/macho_id.cc',
@@ skipping 100 matching lines @@
         '../build/testing.gypi:gmock_main',
         '../build/testing.gypi:gmock',
         '../build/testing.gypi:gtest',
       ],
       'libraries': [
         '-ldl',
       ],
     },
   ],
 }