[OpenMP] Integrate OpenMP target region cubin into host binary

Summary: OpenMP device offloading code generation produces a cubin file which is then integrated in the host binary using the host linker.

Reviewers: arpith-jacob, caomhin, carlo.bertolli, ABataev, Hahnfeld, jlebar, rnk, hfinkel, tstellar

Reviewed By: hfinkel

Subscribers: sfantao, rnk, rengolin, cfe-commits

Differential Revision: https://reviews.llvm.org/D29654

llvm-svn: 310291