[graphite] Add hook for dynamically generated glue code

Bug: skia:12701
Change-Id: I67100f3e182211b7f161d0574d75e8837cfd6835
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/506537
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed