[llvm] [MergeFuncs] Don't introduce calls to (linkonce,weak)_odr functions. (PR #125050)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

I found another case where we would introduce calls to linkonce_odr/weak_odr functions, if we merge 3+ linkonce_odr/weak_odr functions.

To fix this, I updated the order to always ensure that the ODR functions come first.

I also updated the code to replace all direct callers of ODR functions to call the thunk

https://github.com/llvm/llvm-project/pull/125050