Back out of GPU Codegen if NVPTX is not available

Summary:
When enabling GPU codegen in polly, CMake will fail if NVPTX is not a target
supported by the LLVM polly is being built against. In that case, GPU codegen
should be switched off.

Reviewers: Meinersbur, grosser, bollu

Reviewed By: Meinersbur

Subscribers: mgorny, bollu, pollydev, llvm-commits

Differential Revision: https://reviews.llvm.org/D47888

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@334233 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed