[llvm] [llvm-mc][AsmParser] Fix Source location for undefined directional labels. (PR #214654)

[via llvm-commits]

zhangweize9-cyber wrote:

Since the original branch has been lost due to the last operation, I have a small request: could I save my own code as a draft? I'd like to keep it as a small memento.

https://github.com/llvm/llvm-project/pull/214654