.gitea/workflows/check: build with matrix

.gitea/workflows/check.yaml

@@ -1,4 +1,4 @@
-name: "Run nix flake check"
+name: "Build nix flake checks"
 on:
   workflow_dispatch:
   pull_request:
@@ -6,6 +6,13 @@ on:
 jobs:
   build:
     runs-on: debian-latest
+    strategy:
+      matrix:
+        package: [
+          "checkStaticExts",
+          "checkStaticExtsCross",
+          "checkStaticExtsCrossAndroid",
+        ]
     steps:
     - uses: actions/checkout@v6
 
@@ -15,5 +22,5 @@ jobs:
     - name: Install nix
       uses: https://github.com/cachix/install-nix-action@v31
 
-    - name: Nix flake check
-      run: nix flake check -L
+    - name: Nix build check package
+      run: nix build .#checks.x86_64-llinux.${{ matrix.package }} -L