[clang] [llvm] [clang][ssaf] Add the TUSummaryExtractorRegistry (PR #173290)

[Balázs Benics via cfe-commits]

steakhal wrote:

> @steakhal Hi, this change doesn't work in MinGW/Cygwin with `-DCLANG_LINK_CLANG_DYLIB=ON` due to wrong instantiations of `llvm::Registry<...>`. Those hosts require proper declarations of the template instantiations to share data symbols across DLL boundaries.
> Could you take a look?

Hey, I'm not available for the next 24 hours, but if you have a fix then I'm happy to review.
Thanks for the guidance, your insight was really valuable.

https://github.com/llvm/llvm-project/pull/173290