[llvm] [Mips][nanoMIPS] Add initial nanoMIPS target support (PR #223032)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

I'd expect to see some testing in tools/llvm-readobj, since you're adding llvm-readobj support in this PR (via the Object changes, if I'm not mistaken). There's already testing there for other MIPS relocation dumping, for example. There are probably other cases too.

https://github.com/llvm/llvm-project/pull/223032