[libc++] Mark libcpp_deallocate.sh.cpp as UNSUPPORTED instead of XFAIL on AppleClang 9

Some minor versions of AppleClang 9 appear not to fail the test. It's
such a mess that the only sane thing to do is to mark the test as
UNSUPPORTED.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@366606 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed