[llvm] [RISCV][MC] Implement evaluateBranch for auipc+jalr pairs (PR #65480)

[Alexander Richardson via llvm-commits]

arichardson wrote:

In general this looks good to me but I do worry a bit about the performance implications of regularly zeroing all the GPRS. Could you show the impact on disassembly of a large binary (e.g. statically linked clang for riscv?)

https://github.com/llvm/llvm-project/pull/65480