Fix standalone test-suite run.

This patch updates libc++abi's HandleOutOfTreeLLVM.cmake to match
libc++'s -- and more importantly, to fix a bug where llvm-lit wasn't
found/created when libc++abi was built out-of-tree. This prevented
the test suite from running.

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@322768 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed