In WinRT we only use the HLSL code, so the GLSL/ESSL output code
is not necessary and is only adding to our binary size.

BUG=angleproject:1250

Change-Id: I9363ca3981bde50a230f8353c1bcc09f6ea209cb
Reviewed-on: https://chromium-review.googlesource.com/317358Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tryjob-Request: Austin Kinross <aukinros@microsoft.com>
Tested-by: Austin Kinross <aukinros@microsoft.com>