Only emit functions that have bodies.
Don't emit their bodies yet.
Emit them so that callees precede callers.
Bug: tint:3
Change-Id: Ia67ba2fe1d47c7c7d5c290d1d4fc5256fa293b51
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18620
Reviewed-by: dan sinclair <dsinclair@google.com>
