[CMake][libcxxabi] Update the libc++ test module path

The libcxx/test/libcxx Python package has been moved into
libcxx/utils/libcxx in r294651, but libcxxabi's CMakeLists.txt still
looks for the old path.

Differential Revision: https://reviews.llvm.org/D30133

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@295540 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed