Retire bugpoint's -R. hack.

Retire bugpoint's -R. hack.

It got disconnected during the cmake conversion. For Miscompilation.cpp,
it was purely advisory for the user and the ToolRunner.cpp version was
trying to compensate for libs and bins in the same directory, which
hasn't been the case for a very long time.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283022 91177308-0d34-0410-b5e6-96231b3b80d8