WIP: Add meson install --dbg

[xclaesse]

It split debug symbols into a separate file. This is similar to Debian -dbg packages.

Open questions:

• Should we support /Z7 with MSVC to be able to include debug info into object files? Currently MSVC always split debug info.
• Using -fsplit-dwarf reportedly speed up build time, maybe we should not do that at install time after all.
• I think ideally we should have a way to make --tags runtime install stripped binaries and --tags dbg install only splitted debug info.
• --debugdir feels weird because all other dirs are builtin options.

All in all, on 2nd thought, I think handling this solely at install time might have been a mistake. We probably do need configure time option for this.

[jpakkane]

I have long wondered if we should have a separate option for split/nonsplit debug info? Windows users need it for /Z7 because the regular thing fails wich sccache and some other things as well and I seem to recall that using separate debug info files speeds up the build on Linux.

[xclaesse]

@jpakkane I have no idea how that works on Windows to be honest. Are debug files splitted by compiler, or extracted at install like on Linux?

Personally my use-case for this is a project we basically pack the install destdir into a tarball and extract it on devices. By default all binaries are stripped, but I would like to easily create a dbg tarball we could extract on top for developers, without having to ship all new unstripped binaries.

[codecov]

Codecov Report

Merging #10064 (06b99be) into master (253df6f) will decrease coverage by 3.67%.
Report is 1 commits behind head on master.
The diff coverage is 42.22%.

❗ Current head 06b99be differs from pull request most recent head 7efc171. Consider uploading reports for the commit 7efc171 to get more accurate results

@@            Coverage Diff             @@
##           master   #10064      +/-   ##
==========================================
- Coverage   70.20%   66.54%   -3.67%     
==========================================
  Files         218      402     +184     
  Lines       47810    85590   +37780     
  Branches    11382    18827    +7445     
==========================================
+ Hits        33567    56954   +23387     
- Misses      11760    24238   +12478     
- Partials     2483     4398    +1915     

Files Changed	Coverage Δ
mesonbuild/minstall.py	66.96% <31.57%> (+0.80%)	⬆️
mesonbuild/backend/backends.py	88.19% <100.00%> (+2.48%)	⬆️
mesonbuild/coredata.py	83.82% <100.00%> (+0.57%)	⬆️

... and 422 files with indirect coverage changes