[clang] [InstallAPI][Tests] Update tests to be resilient to reversion iteration config (PR #89270)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

How hard would it be to make the output here have a consistent order?  I mean, emitting diagnostics in a consistent order isn't nearly as important as emitting consistent binaries, but it's still nice to have if we can get it easily.

https://github.com/llvm/llvm-project/pull/89270