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

[Saleem Abdulrasool via cfe-commits]

compnerd wrote:

I can see that as being useful certainly. `-fblocks` could add `-lBlocksRuntime`. However, I think that the behaviour change with `-static-libclosure` would then impact both code generation (on Windows) and the linking, which would give the correct desired behaviour. Where as, only changing the linking behaviour would come at the of preventing some optimizations and only linking appropriately.

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