[dsan] Possibly flaky test on AArch64

Hi all,

I've seen the custom.cc test seg-faulting a couple of times on one of our bots:
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-full/builds/1901
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-full/builds/1838

Any idea why this might be happening?

Thanks,
Diana