[OpenMP] Use CUDA's non-RDC mode when LTO has whole program visibility

When we do LTO we consider ourselves to have whole program visibility if
every single input file we have contains LLVM bitcode. If we have whole
program visibliity then we can create a single image and utilize CUDA's
non-RDC mode by not passing `-c` to `ptxas` and ignoring the `nvlink`
job. This should be faster for some situations and also saves us the
time executing `nvlink`.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D124292