[lld] [lld][ELF] Add --debug-names to create merged .debug_names. (PR #86508)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> ant to get in the way of that. My PR for addng support for foreign type units hasn't gone in yet either, so I am happy to change course here. We just need a way to be able ensure that .debug_names entries for foreign type units somehow know if they are valid or not. Our previous attempt at this was to add a DW_AT_dwo_name attribute to the DW_TAG_type_unit and then verify that this matched the one any only CU in the CU list of the .debug_names table, but happy to pivot if we can think of a

Thanks for chiming in. Type units are not handled yet in this patch. This patch focuses on compile units with an opt-in option `--debug-names`. I'll try study your lldb type units implementation:)

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It seems that the remaining issues are minor style issues. LGTM to make it clear I am happy once these issues are resolved or possibly defer some later if @dwblaikie is fine with that.

https://github.com/llvm/llvm-project/pull/86508