os.system uses fork(), which is not supported by ASAN/LSAN. Some fuzz tests
consist of js code that randomly picks properties and functions and calls them.
Sometimes, this combination means ASAN will report false positives.

Bug: chromium:740361
Change-Id: Id8d517263251a1fe88abadd33b0225c664b00498
Reviewed-on: https://chromium-review.googlesource.com/580313Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46876}