[clang] [llvm] [dwarf] make dwarf fission compatible with RISCV relaxations (PR #164128)

[David Blaikie via cfe-commits]

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+; RUN: llc -dwarf-version=5 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
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dwblaikie wrote:

Could you generalize this test with multiple RUN lines to cover the two (DWARFv4, DWARFv5) or three (DWARFv4, DWARFv5, Split DWARFv5) (or perhaps 4, if you wanted to test Split DWARFv4 too) that are affected by this change?

I think we have an existing test somewhere that checks there are no relocations in .dwo files - maybe that's an `assert`, rather than a test, so we can't actually ever produce/observe a .dwo file with relocations? (if we have an existing test somewhere that actually dumps relocations - might be worth reusing that kind of testing here too in the Split DWARF case to validate there are no relocations in the .dwo file)

https://github.com/llvm/llvm-project/pull/164128