[clang] [clang][ssaf] Fix plugin crash on AIX by adding `SUPPORT_PLUGINS` to `clang-ssaf-format` (PR #192292)

[Jake Egan via cfe-commits]

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

Confirmed this fixes the test on AIX. Thank you for the quick fix.

https://github.com/llvm/llvm-project/pull/192292