Create blank SkSL test files for Ninja's benefit.

GN lists both the .cpp and the .h as generated outputs, so if they don't
exist, Ninja assumes we need to rebuild the tests every time we compile.

Change-Id: I37b8b3d9e7aef1b0cb8d5c70530c2542a6c0087a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/317108
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed