haskellPackages.miso-examples: build with js backend

[alexfmpe]

$ nix-build -A pkgsCross.ghcjs.haskell.packages.ghc912.miso-action-logger
/nix/store/q085a26dp38kzjy0q2pyghgzfblnv1rc-miso-action-logger-0.1.0.1
$ nix-build -A pkgsCross.ghcjs.haskell.packages.ghc912.miso-examples
/nix/store/2r9dqw1phig9m8ldk1rvfk21wi6a05nf-miso-examples-1.8.7.0

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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[sternenseemann]

I suppose we bump hackage a little again? dmjio/miso#740 (comment)

[sternenseemann]

#380707 has miso-examples-1.8.6.0. Stackage LTS still restricts miso to 1.8.5.0, but it could be manually upgraded.

[dmjio]

I'm going to push 1.8.7 now, per a CPP fix made today in order for miso-examples to compile without that patch (in this PR).

[alexfmpe]

Confirmed this builds with the 1.8.7 versions.
Given miso-examples doesn't actually run yet with pkgsCross.ghcjs (some linking stuff ?) and it's not a library, I'm drafting until we next bump hackage.

[maralorn]

LGTM

Maybe a hydra job for this would be cool. But not in this PR.