fuzzing: add -fno-builtin when fuzzing with Centipede

According to some recent information, Centipede performs better when
being able to intercept functions such as memcpy, memcmp etc..

Bug: 330758175
Change-Id: I255fce6eefc8f8ab603915e746af23c47dbaccf4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5397540


Auto-Submit: Paul Semel <paulsemel@chromium.org>
Commit-Queue: Paul Semel <paulsemel@chromium.org>
Reviewed-by: Adrian Taylor <adetaylor@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1279091}