[SE] Let users specify CUDA path Summary: Add logic to allow users to specify the CUDA path at configuration time. Reviewers: jlebar Subscribers: beanz, mgorny, jlebar, jprice, parallel_libs-commits Differential Revision: https://reviews.llvm.org/D24580 llvm-svn: 281626 GitOrigin-RevId: b2d62bd071c6e005483c9fa5b917d7261295eb0c