Make fuzz broadcast when it terminates via return.

This helps analysis figure out things like timeouts and unexpected, uncaught
exits.

TBR=mtkelin@google.com
BUG=skia:4438
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1657743002

Review URL: https://codereview.chromium.org/1657743002
1 file changed