[clang] [clang][ssaf] Workaround gcc-7 NRVO bug (PR #186897)

[Balázs Benics via cfe-commits]

steakhal wrote:

This is like the 3rd time we hit this gcc bug. I'm sure you remember @pawosm-arm.
I look forward to the day we raise the bar get some relief from this gcc bug.

FYI: I'll be out -- well, sleep some. So if you decide to merge this, look out for revert requests, because I won't!

https://github.com/llvm/llvm-project/pull/186897