[lld] [llvm] [DTLTO] Delay individual bitcode file serialization until after cache checks (PR #191142)

[Konstantin Belochapka via llvm-commits]

kbelochapka wrote:

@bd1976bris This is an excellent idea - skip saving input bitcode archive members if the corresponding native object file has already been cached. However, implementing this feature in the refactored code is much less complex and takes only few lines of code.  

https://github.com/llvm/llvm-project/pull/191142