chmod +x python builds scripts, run directly instead of with python gyp var

gyp/shaders.gypi

@@ -16,7 +16,7 @@
             '<(SHARED_INTERMEDIATE_DIR)/src/shader/shaders_gl.cpp',
             '<(SHARED_INTERMEDIATE_DIR)/src/shader/shaders_gles2.cpp',
           ],
-          'action': ['<@(python)', 'scripts/build-shaders.py', '<(SHARED_INTERMEDIATE_DIR)', '<@(_inputs)'],
+          'action': ['scripts/build-shaders.py', '<(SHARED_INTERMEDIATE_DIR)', '<@(_inputs)'],
         }
       ],
       'direct_dependent_settings': {

gyp/version.gypi

@@ -13,7 +13,7 @@
           'outputs': [
             '<(SHARED_INTERMEDIATE_DIR)/include/mbgl/util/version.hpp',
           ],
-          'action': ['<@(python)', '<@(_inputs)', '<(SHARED_INTERMEDIATE_DIR)', '<!@(git describe --tags --always --abbrev=0)', '<!@(git rev-parse HEAD)'],
+          'action': ['<@(_inputs)', '<(SHARED_INTERMEDIATE_DIR)', '<!@(git describe --tags --always --abbrev=0)', '<!@(git rev-parse HEAD)'],
         }
       ],
       'direct_dependent_settings': {