Starting a test case with `// flags: <flags>` will
append the <flags> to the tint executable for that test case.
Let's you specify things like `// flags: --transform XXX`, which lets us
end-to-end test a particular set of transforms.
Change-Id: I181e9f7e7c1fba5e3a47cf58aee462b51e4b6e3b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/60921
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>