[llvm] [ARM] Use .reloc for weak symbols in PIC mode instead of GOT indirection (PR #208372)

[Peter Smith via llvm-commits]

https://github.com/smithp35 commented:

Agreed that this way is better than using the GOT. I've checked that the assembler output also works with GNU as.

A couple of small comment suggestions, and one test suggestion, but otherwise looks good to me. I've added a couple of extra ARM backend reviewers in case they want to comment.

https://github.com/llvm/llvm-project/pull/208372