[lld] [llvm] [RISCV] Teach RISCVMergeBaseOffset to merge %lo into load/store folding arithmetic (PR #185353)

[via llvm-commits]

LiqinWeng wrote:

Considering that some users will use clang + gnu ld, I have also implemented it in binutils, and I will upload a commit later.

https://github.com/llvm/llvm-project/pull/185353