ci/bindings: remove platform-matrix code

.github/workflows/build-bindings.yml

@@ -6,31 +6,15 @@ name: Build o1js bindings
 
 on:
   pull_request:
-  push:
 
-jobs:
-  nix-matrix:
+jobs:  
+  nix-build:
+    name: build-bindings-ubuntu
     runs-on: ubuntu-latest
-    outputs:
-      matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
       - uses: actions/checkout@v4
       - uses: cachix/install-nix-action@v30
-      - id: set-matrix
-        name: Generate Nix Matrix
-        run: |
+      - run: |
           set -Eeu
-          matrix="$(nix eval --json '.#githubActions.matrix')"
-          echo "matrix=$matrix" >> "$GITHUB_OUTPUT"
-
-  nix-build:
-    name: ${{ matrix.name }} (${{ matrix.system }})
-    needs: nix-matrix
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix: ${{fromJSON(needs.nix-matrix.outputs.matrix)}}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v30
-      - run: ./pin.sh
-      - run: 'nix develop o1js --command bash --command "npm run build:bindings && npm run build:update-bindings"'
+          ./pin.sh
+          nix develop o1js --command bash --command "npm run build:bindings && npm run build:update-bindings"

flake.nix

@@ -12,8 +12,10 @@
     dune-nix.inputs.nixpkgs.follows = "nixpkgs";
     dune-nix.inputs.flake-utils.follows = "flake-utils";
     flake-utils.url = "github:numtide/flake-utils";
+    nix-github-actions.url = "github:nix-community/nix-github-actions";
+    nix-github-actions.inputs.nixpkgs.follows = "nixpkgs";
   };
-  outputs = { self, nixpkgs, flake-utils, ... }@inputs:
+  outputs = { self, nixpkgs, nix-github-actions, flake-utils, ... }@inputs:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs= (nixpkgs.legacyPackages."${system}".extend