[orc] Add a trivial unit test to get the ball rolling

[orc] Add a trivial unit test to get the ball rolling

I made my best guess at the Makefile, since I don't have a make build.

I'm not sure if it should be valid to add an empty list of things, but
it seemed the sort of degenerate case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230196 91177308-0d34-0410-b5e6-96231b3b80d8