[llvm] [llvm-dwp] turn duplicate dwo id into warning, continue to gen dwp (PR #121193)

[Alexander Yermolovich via llvm-commits]

ayermolo wrote:

Is there a case for it to be a warning, other then binutils does it?
One way of looking at it, this will produce incomplete, broken(?), debug information, and in big build systems people just ignore warnings.

https://github.com/llvm/llvm-project/pull/121193