The old LLVM pass manager is deprecated and should not be used anymore.
Moreover, the pass manager builder (which we used to set up a pass
pipeline) is actually removed from LLVM entirely in LLVM 17:
https://reviews.llvm.org/D145387https://reviews.llvm.org/D145835
The new pass manager does change the binary size in many cases: both
growing and shrinking it. However, on average the binary size remains
more or less the same.
This is needed as a preparation for LLVM 17.