Fix darwin-ld-lto test for some speical path

Fix the test by not assuming the prefix path of the temp directory can
be matched by a regex.

rdar://problem/56259195

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@375027 91177308-0d34-0410-b5e6-96231b3b80d8