[llvm] [offload][flang-rt] Fix NVPTX runtime build (PR #180530)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

Was there a recent change here? I thought this worked, and if the check fails then I'd expect `flang-rt` to correctly disable whatever's failing.

https://github.com/llvm/llvm-project/pull/180530