Reapply: rav1e: remove build-time dependency on libgit2

[paparodeo]

re-apply #355325 which is a better way to de-vendor libgit2 but had to be reverted on master due to mass-builds.

files are identical after this PR and #355325

$ curl -sL https://raw.githubusercontent.com/NixOS/nixpkgs/fab8f4325c0534d7d63d46a2fafe89cee5e29e46/pkgs/by-name/ra/rav1e/package.nix | md5sum
9804aef983596bd180816aef52172c28  -
$ curl -sL https://raw.githubusercontent.com/NixOS/nixpkgs/c4a4f958cb5af702f61f88d0e762af1700c6a705/pkgs/by-name/ra/rav1e/package.nix|md5sum
9804aef983596bd180816aef52172c28  -

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

---

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@emilazy
@tjni

[getchoo]

Built against nixos-unstable and everything works as expected. Thanks!

[paparodeo]

eval breakage seems due to #354738
@ofborg eval

[tjni]

Thank you for following up on this!

[nixpkgs-ci]

Backport failed for staging-24.11, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin staging-24.11
git worktree add -d .worktree/backport-360999-to-staging-24.11 origin/staging-24.11
cd .worktree/backport-360999-to-staging-24.11
git switch --create backport-360999-to-staging-24.11
git cherry-pick -x b80ae990684936b8c84825e27929cb5b11483dec