Fix tsan test for Darwin. NFCI.
Fix tsan test for Darwin. NFCI.

On Darwin, strerror_r returns an int, not a char*. I don't think this
test really depends on what strerror_r returns, so I've used something
else in place of the result of the call to strerror_r.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@304941 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