GYP groudwork for half-float opts support.

gyp/opts.gypi

Index: gyp/opts.gypi
diff --git a/gyp/opts.gypi b/gyp/opts.gypi
index dfcf434aff222976d49bbc6894f26a4cedef1a6f..9e1f63ea859f7bdcb704693eb3d923cc3d8c69b9 100644
--- a/gyp/opts.gypi
+++ b/gyp/opts.gypi
@@ -33,6 +33,8 @@
             '<(skia_src_path)/opts/memset16_neon.S',
             '<(skia_src_path)/opts/memset32_neon.S',
         ],
+        'neon_fp16_sources': [
+        ],
         'arm64_sources': [
             '<(skia_src_path)/opts/SkBitmapProcState_arm_neon.cpp',
             '<(skia_src_path)/opts/SkBitmapProcState_matrixProcs_neon.cpp',
@@ -81,4 +83,6 @@
             '<(skia_src_path)/opts/SkBlurImage_opts_SSE4.cpp',
             '<(skia_src_path)/opts/SkBlitRow_opts_SSE4.cpp',
         ],
+        'avx_sources': [
+        ],
 }