Fix linux dependency making into osx, windows

main.scons

 # Copyright 2009, 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
@@ skipping 644 matching lines @@
 environment_list.append(mac_test_optimized_env)
 
 # Linux ------------------------------------------------------------------
 
 linux_env = binaries_env.Clone(
     tools = ['target_platform_linux'],
     FIREFOX_PLUGIN_DIR = '/home/$USER/.mozilla/plugins',
     CG_DIR = '$CG_BASE_DIR/linux',
 )
 linux_env.FilterOut(CPPDEFINES = ['OS_LINUX=OS_LINUX'])
-linux_env.ParseConfig('pkg-config --cflags --libs gtk+-2.0')
+if base_env.Bit('host_linux'):
+  linux_env.ParseConfig('pkg-config --cflags --libs gtk+-2.0')
 
 linux_env.Append(
     RENDERER_INCLUDE_PATH = [
         '$GLEW_DIR/include',
         '$CG_DIR/include',
     ],
     RENDERER_LIB_PATH = [
         '$CG_DIR/lib',
         '$GLEW_DIR/lib',
     ],
@@ skipping 155 matching lines @@
     'o3d', environment_list,
     exclude_pattern = '.*third_party.*',
     extra_build_targets = {
         'Firefox': 'c:/Program Files/Mozilla FireFox/firefox.exe',
         'unit_tests': '$ARTIFACTS_DIR/unit_tests.exe',
         'system_tests': '$ARTIFACTS_DIR/system_tests.exe',
         'converter': '$ARTIFACTS_DIR/o3dConverter.exe',
     },
 )
 solution_env.Alias('solution', solution)