[Infrastructure] Use -gsplit-dwarf to improve linking

[ktf]

No description provided.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 0 warnings, 🔕 0 disabled

[ktf]

In my minimal test seems to speed up building by 15%.

[alibuild]

Error while checking build/O2Physics/o2 for 7147fe1 at 2026-02-17 12:53:

## sw/BUILD/O2Physics-latest/log
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
c++: error: unrecognized debug output level 'split-dwarf=single'
ninja: build stopped: subcommand failed.

Full log here.

[vkucera]

@ktf The option -gsplit-dwarf does not seem to take any arguments.

[ktf]

Indeed... It's only supported by Clang... :-/ We can have the version without the option, however it will mean that we have to do some extra juggling to get the debug symbols working.

[vkucera]

Indeed... It's only supported by Clang... :-/ We can have the version without the option, however it will mean that we have to do some extra juggling to get the debug symbols working.

Isn't it enough to just use the Clang version for macOS and the GCC version for Linux?

[ktf]

This is only for linux (Clang and Linux), on macOS the debug symbols are handled in a different way (via .dSYM) and this does not really apply.

The GCC version will need some extra juggling in any case to allow the debugger to find the debug symbols. The nice thing of =single, AFAICT, is that there is still only one file (hence the name). Still, the debug information is completely separate with such an option from the elf layout point of view and the linker does way less heavy lifting to merge multiple objects.