[llvm-branch-commits] ELF: Use preprocessed relocations for EhInputSection scanning (PR #161091)

[Fangrui Song via llvm-branch-commits]

https://github.com/MaskRay created https://github.com/llvm/llvm-project/pull/161091

.eh_frame sections require special sub-section processing, specifically,
CIEs are de-duplicated and FDEs are garbage collected. Create a
specialized scanEhSection() function utilizing the just-added
EhInputSection::rels. OffsetGetter is moved to scanEhSection.

This improves separation of concerns between InputSection and
EhInputSection processing.

This removes another `relsOrRelas` call using `supportsCrel=false`.
DWARF.cpp now has the last call.