[clang] [llvm] [Clang] Invoke pass plugin preCodeGenCallback (PR #171872)

[Alexis Engelke via llvm-commits]

aengelke wrote:

@grigornik Done with ad2c2b2b1c6bb95f58150cdf172785cabef40d4a. There's also #174006, in which I now also marked the tests as xfail on AIX.

https://github.com/llvm/llvm-project/pull/171872