[clang] [lld] [llvm] [LTO] enable `ObjCARCContractPass` only on optimized build (PR #101114)

[Peter Rong via cfe-commits]

DataCorrupted wrote:

> Is there some way we can avoid the additional domtree construction? Particularly in cases where the pass doesn't do anything.

This patch only changes how the pass is called. The behavior of the pass itself is probably another patch. Besides, I don't think it would be easy for `PassConfig` to get a hold of the module that we are compiling.

https://github.com/llvm/llvm-project/pull/101114