[libc] Fix using the `libcgpu.a` for NVPTX in non-LTO builds

CUDA requires a PTX feature to be compiled generally, because the
`libcgpu.a` archive contains LLVM-IR we need to have one present to
compile it. Currently, the wrapper fatbinary format we use to
incorporate these into single-source offloading languages has a special
option to provide this. Since this was not present in the builds, if the
user did not specify it via `-foffload-lto` it would not compile from
CUDA or OpenMP due to the missing PTX features. Fix this by passing it
to the packager invocation.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D154864