[lld] [lld][ELF] Support relax R_LARCH_{ALIGN, PCALA_{HI20,LO12}, GOT_PC_{HI20,LO12}} (PR #78692)

[Xi Ruoyao via llvm-commits]

xry111 wrote:

> Basically looks good to me. Thanks. @MaskRay What do you think about this change? If looks OK, do you mind merging this before 18.x is created or cherry-picking later? As gcc/binutils have began generating relax relocations for about 1 year, lld needs this PR so that it can link fundamental system objects (such as `Scrt1.o`).

IMO at least supporting R_LARCH_RELAX should be considered a bug fix and it should be in 18.x, or we are basically shipping "unusable" things.

https://github.com/llvm/llvm-project/pull/78692