font-manager: fix build issue

[ShowhyT]

Closes: #557142

Fix build issue with newer vala versions via a patch. Fetched the patch from this PR:
FontManager/font-manager#468

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.
• Follows the automation/AI policy.

[ShowhyT]

✅ nixpkgs-review result for #557155

Generated using nixpkgs-review-gha (85088ce)

Command: nixpkgs-review pr 557155
Commit: 6cf9465b65ee6e9a9015394a932d142f88cb72b9 (subsequent changes)
Merge: 7f0b54b06c88be659c5c45db27d8f24582c07f2d

Logs: https://github.com/ShowhyT/nixpkgs-review-gha/actions/runs/33158996470/attempts/1

Download packages from cache:

• x86_64-linux

  nix-store -r \
    --option binary-caches 'https://cache.nixos.org/ https://builds.cachix.org' \
    --option trusted-public-keys '
      cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
      builds.cachix.org-1:628RFN/JZH6b09pwud65gIAvYg9oGIEGIqNPy8cDRU4=
    ' \
    /nix/store/088270ibmrxkjxrkzsjg9w759g59s7sn-font-manager-0.9.4

• aarch64-linux

  nix-store -r \
    --option binary-caches 'https://cache.nixos.org/ https://builds.cachix.org' \
    --option trusted-public-keys '
      cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
      builds.cachix.org-1:628RFN/JZH6b09pwud65gIAvYg9oGIEGIqNPy8cDRU4=
    ' \
    /nix/store/18blf7ih1wimyn7i7gay05jv93j0x8jn-font-manager-0.9.4

---

x86_64-linux

✅ 1 package built:

• font-manager

---

aarch64-linux

✅ 1 package built:

• font-manager

[romildo]

LGTM

[thunze]

• Diff LGTM
• Verified that the package builds on x86_64-linux
• Verified basic functionality of the package on x86_64-linux

Thanks!

[amarshall]

Duplicate of #556842

[nixpkgs-ci]

Successfully created backport PR for release-26.05:

• [Backport release-26.05] font-manager: fix build issue #558348