The fuzzer function is called multiple times with libfuzzer. Trap
handlers, however, should only be initialized once. With this CL we add
a flag to initialize trap handlers only once.

R=clemensb@chromium.org

Bug: chromium:1122590
Change-Id: Ib51a50cfe9dad5e3133de3085ad147f5a069b1bd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2384769
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69643}