[clang] [HIP] Allow partial linking for `-fgpu-rdc` (PR #81700)

[Artem Belevich via cfe-commits]

https://github.com/Artem-B approved this pull request.

Overall LGTM. Please wait for @jhuber6's to double check the partial linking mechanics details.

https://github.com/llvm/llvm-project/pull/81700