Pull and build shaderc rather than use checked in lib/header

gyp/shaderc.gyp

+# Copyright 2016 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Builds shaderc for the Vulkan backend
+{
+  'variables': {
+    'conditions': [
+      [ 'CONFIGURATION_NAME == "Release_Developer"', {
+        'shaderc_build_type' : 'Release',
+      }, {
+        'shaderc_build_type' : '<(CONFIGURATION_NAME)',
+      }],
+      [ 'skia_os == "win"', {
+        'shaderc_lib_name' : 'shaderc_combined.lib',
+      }, {
+        'shaderc_lib_name' : 'libshaderc_combined.a',
+      }],
+      [ 'MSVS_VERSION == "2013"', {
+        'shaderc_project_type' : 'MSVS2013',
+      }],
+      [ 'MSVS_VERSION == "2015"', {
+        'shaderc_project_type' : 'MSVS2015',
+      }],
+    ],
+    'skia_build_type' : '<(CONFIGURATION_NAME)',
+  },  
+  'targets': [  
+    {
+      # Call out to a python script to build shaderc_combined and then copy it
+      # to out/<Configuration>
+      'target_name': 'shaderc_combined',
+      'type': 'none',
+      'actions': [
+        {
+          'action_name': 'compile_shaderc',
+          'inputs': [
+            '<!@(python find.py ../third_party/externals/shaderc2 "*")',
+            '../tools/build_shaderc.py',
+          ],
+          'outputs': [
+             '../out/<(skia_build_type)/shaderc_out_<(skia_arch_type)/libshaderc/<(shaderc_build_type)/<(shaderc_lib_name)',
+          ],
+          'action': ['python', '../tools/build_shaderc.py', '-s', '../third_party/externals/shaderc2', '-o', '../out/<(skia_build_type)/shaderc_out_<(skia_arch_type)', '-a', '<(skia_arch_type)', '-t', '<(shaderc_build_type)', '-p', '<(shaderc_project_type)'],
+        },
+      ],     
+      'copies': [
+        {
+          'destination': '../out/<(skia_build_type)',
+          'files': ['../out/<(skia_build_type)/shaderc_out_<(skia_arch_type)/libshaderc/<(shaderc_build_type)/<(shaderc_lib_name)'],
+        },
+      ],
+      'all_dependent_settings': {
+        'link_settings': {
+          'libraries': [
+            '-lshaderc_combined',
+          ],
+        },
+      },
+    },
+  ],
+}