[test] Disable leak checking on a clang crash test on Darwin

Suspected failure due to LSan's atexit and exit interception behavior.

Reviewers: kcc, kubamracek, bogner, hfinkel, alekseyshl, Hahnfeld, gtbercea

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37810

llvm-svn: 314526