add hello-opencl

This is a little hello world for OpenCL.

Change-Id: I9502407dab75694a19e97832bcfe33f47cbd97e9
Reviewed-on: https://skia-review.googlesource.com/136223
Commit-Queue: Allan MacKinnon <allanmac@google.com>
Reviewed-by: Allan MacKinnon <allanmac@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 3fa9344..f3f170e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -26,6 +26,7 @@
   skia_use_libpng = true
   skia_use_libwebp = !is_fuchsia
   skia_use_lua = is_skia_dev_build && !is_ios
+  skia_use_opencl = false
   skia_use_piex = !is_win
   skia_use_zlib = true
   skia_use_metal = false
@@ -2177,4 +2178,16 @@
       ]
     }
   }
+
+  if (skia_use_opencl) {
+    test_app("hello-opencl") {
+      sources = [
+        "src/compute/common/cl/assert_cl.c",
+        "src/compute/common/cl/find_cl.c",
+        "tools/hello-opencl.cpp",
+      ]
+      include_dirs = [ "src/compute/common" ]
+      libs = [ "OpenCL" ]
+    }
+  }
 }