compiler-rt: Rename .cc file in test/xray to .cpp

Like r367463, but for test/xray.

Update test/xray/lit.cfg.py config.suffixes to remove .cc (we actually
don't have .c tests now)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@367652 91177308-0d34-0410-b5e6-96231b3b80d8
29 files changed