run the webtry build script instead of using go build

BUG=skia:
R=jcgregorio@google.com

Author: humper@google.com

Review URL: https://codereview.chromium.org/601203002

experimental/webtry/setup/continue_install

@@ -53,9 +53,9 @@ git checkout master
 # git apply $PATCH
 
 GYP_GENERATORS=ninja ./gyp_skia gyp/webtry.gyp gyp/most.gyp -Dskia_gpu=0
-ninja -C out/Debug webtry
+ninja -C out/Release webtry
 
 cd experimental/webtry
 
 go get -d
-go build webtry.go
+./build