Tracking issue for `-Zdwarf-version`

[pnkfelix]

This is a tracking issue for the -Zdwarf-version unstable flag (no RFC/MCP) added in #98350 which allows selecting the specific version of DWARF to use when creating debuginfo.

About tracking issues

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A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
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Steps

• Initial implementation (Implement support for DWARF version 5. #98350)
• Wider Testing (tested on RfL)
• Adjust documentation (see instructions on rustc-dev-guide) (Stabilize -Zdwarf-version as -Cdwarf-version #136926)
• Stabilization PR (see instructions on rustc-dev-guide) (Stabilize -Zdwarf-version as -Cdwarf-version #136926)

Unresolved Questions

• Is the pre-compiled standard library (potentially) using a different version of DWARF an issue?
• What should the behavior of the flag do when the active target does not use DWARF?

Implementation history

• Initial implementation: Implement support for DWARF version 5. #98350
• Stop emitting .debug_pubnames and .debug_pubtypes when using DWARF 5 fix: stop emitting .debug_pubnames and .debug_pubtypes #117962
• Refactoring & cleanups Clean up uses of the unstable dwarf_version option #135739
• Fix LLVM warning on LTO with different DWARF versions Pick the max DWARF version when LTO'ing modules with different versions  #136659
• Improve argument validation Emit an error if -Zdwarf-version=1 is requested #136746

[thomcc]

Ideally this design proposal would include some method of exposing it to cargo build scripts, so crates like cc would be able to use the right version of DWARF (see rust-lang/cc-rs#694, for example, where we hardcode decisions compatible with rustc)

[Wyvern]

Is there a unstable way to opt-in DWARF5 for Rust now?
Tried -Zdwarf-version=5 in macOS, but seems failed.