[llvm] [offload][runtimes] Forward user-provided system configuration. (PR #96303)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Seems like a generalisation of the code already added for libc, so no objections from me here.

@jhuber6 should be the approver, as the author of the original code.

https://github.com/llvm/llvm-project/pull/96303