Fix SkSL standalone build

Change-Id: I66713976f08b1dbf0966d9a901f666b9f834b659
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/221096
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed