[lld] [ELF] Fix -u with TLS symbols: propagate type from STT_NOTYPE to STT_TLS (PR #185794)

[Peter Smith via llvm-commits]

https://github.com/smithp35 approved this pull request.

LGTM thanks.

Running the test case in https://github.com/llvm/llvm-project/pull/178846 against gnu ld, it seems like the symbol retains the STT_TLS type, although I don't know what the underlying mechanism is.

I did think of the case where the reference in the object file has weak binding, but the reference from -u will be non-weak. Could there be a reason not to transfer the file and symbol type in that case? 

The combination will be a non-weak reference from the file with symbol type STT_TLS. I think that is going to be fine in most practical cases. Only thing that I think could go wrong is that any error message we get about undefined symbols (from non-weak binding) will refer to the weak-reference from the object which could be confusing. However I think that is better than getting a relocation out of range error.

https://github.com/llvm/llvm-project/pull/185794