Add gen_interface to CheckGeneratedFiles check Checked that it properly fails on PS2 Change-Id: Ieff2e035a18cd5572dfe3a20a58bd760477a2b62 Bug: skia: Reviewed-on: https://skia-review.googlesource.com/c/skia/+/204446 Reviewed-by: Eric Boren <borenet@google.com> Commit-Queue: Kevin Lubick <kjlubick@google.com>