[ASan] Fix stack-overflow test for PowerPC
[ASan] Fix stack-overflow test for PowerPC

Summary:
Tweak the asan stack overflow heuristics to cope with PowerPC64 redzones,
which are larger than on x86-64: 288 bytes for big-endian and 512 bytes
for little-endian.

Reviewers: kcc, willschm, samsonov, eugenis

Reviewed By: samsonov, eugenis

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6168

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@221578 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt