Add permittedLayoutFlags to checkModifiers

For now, just use this to prevent *any* layout qualifiers from appearing
on functions, or their parameters.

Bug: skia:11301
Change-Id: I05d8118c7121048c6ef49695a54e3714a8f8687e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/376796
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
5 files changed