This attribute is used to ensure the guard page is triggered on stack
overflow. Stack frames larger than the guard page size will generate
a call to __probestack to touch each page so the guard page won't
be skipped.
Reviewed By: majnemer
Differential Revision: https://reviews.llvm.org/D34386
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305939 91177308-0d34-0410-b5e6-96231b3b80d8
