Enforce better header hygiene

Apple recommends disabling ALWAYS_SEARCH_USER_PATHS, so we now do. And we also
disable USE_HEADER_MAP to match other platforms more closely.

brightray/brightray.gypi

@@ -10,6 +10,7 @@
       'NDEBUG',
     ],
     'xcode_settings': {
+      'ALWAYS_SEARCH_USER_PATHS': 'NO',
       'CLANG_CXX_LANGUAGE_STANDARD': 'gnu++11',
       'CLANG_CXX_LIBRARY': 'libstdc++',
       'COMBINE_HIDPI_IMAGES': 'YES',
@@ -18,6 +19,7 @@
       'MACOSX_DEPLOYMENT_TARGET': '10.7',
       'RUN_CLANG_STATIC_ANALYZER': 'YES',
       'SDKROOT': 'macosx10.7',
+      'USE_HEADER_MAP': 'NO',
       'WARNING_CFLAGS': [
         '-Wall',
         '-Wextra',