[clang] [clang][SSAF] Propagate parent linkage to sub-entity decls (PR #201971)

[Balázs Benics via cfe-commits]

steakhal wrote:

I already reviewed #201946 with the same content.
Can we close this in favour of that one?
That also has a radar in the PR summary.

https://github.com/llvm/llvm-project/pull/201971