Fix check-llvm on kernel 4.9+ with asan or msan

Summary:
Before https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.9.46&id=84638335900f1995495838fe1bd4870c43ec1f67
test worked because memory allocated with mmap was not counted against RLIMIT_DATA.

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37366

llvm-svn: 312303