[llvm] [dwarf] make dwarf fission compatible with RISCV relaxations 1/2 (PR #166597)

[Jeremy Morse via llvm-commits]

jmorse wrote:

Drive by comment -- I believe your assessment @dlav-sc is totally correct, about the purposes of absoluteSymbolDiff and isRangeRelaxable. I've run into similar issues in #134677 . AFAIUI the RISC-V linetable is emitted slightly inefficiently because of this distinction. (I don't have anything to say about this PR, but figured I'd confirm the understanding in the comment above).

https://github.com/llvm/llvm-project/pull/166597