The flag should not be set after an exception is thrown in a runtime
function. The unwinder still runs after the destructor, and should take
care of setting the flag depending on the catching frame.

R=ahaas@chromium.org,jkummerow@chromium.org

Bug: chromium:1180690
Change-Id: I0013c90f759a5145309f6e08d61ed36aeecbac63
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2713103Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72972}