[clang] [Driver] Link Flang runtime on FreeBSD, NetBSD, OpenBSD, DragonFly and Haiku (PR #69817)

[Fangrui Song via cfe-commits]

https://github.com/MaskRay approved this pull request.

LGTM, but [banach-space](https://github.com/banach-space) should check as well.


https://github.com/llvm/llvm-project/pull/69817