[clang] CodeGen: support static linking for libclosure (PR #125384)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

Please add HelpText for the new option. Maybe mention in that text that it currently doesn't affect linking.

Please add a release note.

Otherwise looks fine.

https://github.com/llvm/llvm-project/pull/125384