add -Iinclude/private anywhere we have -Isrc/core

gyp/gpu.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 # GYP for building gpu
 {
   'target_defaults': {
     'conditions': [
       ['skia_os != "win"', {
         'sources/': [ ['exclude', '_win.(h|cpp)$'],
@@ skipping 76 matching lines @@
         'core.gyp:*',
         'utils.gyp:utils',
         'etc1.gyp:libetc1',
         'ktx.gyp:libSkKTX',
       ],
       'includes': [
         'gpu.gypi',
       ],
       'include_dirs': [
         '../include/gpu',
+        '../include/private',
         '../src/core',
         '../src/gpu',
         '../src/image/',
       ],
       'sources': [
         '<@(skgpu_sources)',
         '<@(skgpu_native_gl_sources)',
         '<@(skgpu_angle_gl_sources)',
         '<@(skgpu_mesa_gl_sources)',
         '<@(skgpu_debug_gl_sources)',
@@ skipping 112 matching lines @@
             'libraries': [
               '-lGLESv2',
               '-lEGL',
             ],
           },
         }],
       ],
     },
   ],
 }