[llvm] [MC][DebugInfo] Emit linetable entries with known offsets immediately (PR #134677)

[Jeremy Morse via llvm-commits]

jmorse wrote:

Ah -- actually I think I see what's going on with that test. It has portions in .debug_line that cross an `isLinkerRelaxable` boundary /and/ it has portions of .debug_line that are fixed-width. Some parts change, while some do not.

With that in mind, I'll remove the `requiresDiffExpressionRelocations` hook I added to this PR, pre-commit a version of dwarf-riscv-relocs.ll that uses `llvm-dwarfdump -debug-line -v` for more verbose output, then rebase so that this PR illustrates exactly what changes in that test. Right now the only visible difference is in the size of .debug_line, but the encoding is what's important.

https://github.com/llvm/llvm-project/pull/134677