melpa: use newer package-build.el to work around a breaking change in Emacs 30

[leungbk]

package--prepare-dependencies has been renamed in a recent revision of
Emacs 30.

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Description of changes

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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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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[leungbk]

Are we still allowed to target master with Elisp updates, or do we now have to target staging?

[AndersonTorres]

Use staging until we have a less worse idea.

(yes I am still disappointed on this...)

[leungbk]

@AndersonTorres OK, done.

[leungbk]

I have pushed an additional commit to avoid using patches entirely and instead use the latest upstream package-build (which now has the appropriate workaround for Emacs 30).

There have been multiple incompatible changes in upstream package-build; I noticed that package-build--package will, unlike before, call package-build-checkout-function and package-build-cleanup-function. I set them both to ignore in order to preserve the semantics of what we had before (I assume Nix takes care of both fetching/checkout and cleanup).

I tested briefly by building Emacs 30 with some packages across a couple of revisions of the overlay (including an overlay commit, temporarily reverted only because it requires a change similar to what is in this PR, containing the upstream Emacs change that motivated this PR).

[Vonfry]

conflict and duplicate with #276943?