harfbuzz: cross compilation

[Mindavi]

Motivation for this change

Support cross-compilation by disabling introspection. Tested by building for aarch64-multiplatform.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[Mindavi]

cc @sternenseemann since he did the last big change (change of build system) for harfbuzz.

[sternenseemann]

Is it impossible to cross-compile gobject-introspection or with gobject-introspection-support? Or is it just not possible in nixpkgs. A comment explaining the situation would be helpful.

[Mindavi]

In the future it might become possible due to the work of @Ericson2314 here: #88222. See also the related issue: #72868.

However, in the present day it's not possible and I think John Ericson is working hard to get the support upstream to prevent having to maintain a fork. It seems like upstream is not very willing to accept the patches though, so the process seems to be slow. As you can see in the PRs, the support is also not complete, so there's some work to do on that.

Any comments on this @Ericson2314 ? This is just my own interpretation of what's happening.

So in short: it's not possible right now, but might be in the future.

[sternenseemann]

Ah, thanks for the explanation! Could you link the related issue or PR with a short note in a comment? I think this makes it clearer to the reader what is going on.

[Mindavi]

I'd rather put it in the commit message to prevent adding that comment on all places that disable introspection (there are at least ~15 or so). But either way is fine by me :).

[sternenseemann]

Sure!

[sternenseemann]

@ofborg build pkgsCross.aarch64-multiplatform.harfbuzz

[Ericson2314]

Suggested change

	(mesonFeatureFlag "introspection" (stdenv.buildPlatform == stdenv.hostPlatform))
	(mesonFeatureFlag "introspection" withIntrospection)

[Ericson2314]

Yes, I am blocked for gobject-introspection on upstream merging PRs for like a year now: https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/227 and https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/224. They even approved the first one. No idea what the deal is; it's been frustrating.

[Mindavi]

Updated to address all comments. Glad we could find a nice solution. Thanks for reviewing! (and great to see that some stuff from Ericson2314 has finally been merged upstream on gobject-introspection, great step in the right direction 😄).