build(ci): add check job & improve build

.gitlab-ci.yml

@@ -3,14 +3,26 @@ image: nixos/nix:2.9.1
 variables:
   NIX_CONFIG: "experimental-features = nix-command flakes"
 
+before_script:
+  - nix-env -iA cachix -f https://cachix.org/api/v1/install
+  - cachix use felschr
+
+stages:
+  - test
+  - build
+
+check:
+  stage: test
+  script:
+    - cachix watch-exec felschr nix flake check
+
 build:
   stage: build
-  allow_failure: true
-  before_script:
-    - nix-env -iA cachix -f https://cachix.org/api/v1/install
-    - cachix use felschr
   script:
-    - cachix watch-exec felschr nix build .#nixosConfigurations.home-pc.config.system.build.toplevel
+    - cachix watch-exec felschr nix build .#deconz
     - cachix watch-exec felschr nix build .#nixosConfigurations.home-server.config.system.build.toplevel
+    # disabled because GitLab.com runner runs out of space
+    # - cachix watch-exec felschr nix build .#nixosConfigurations.home-pc.config.system.build.toplevel
   only:
     - main
+  allow_failure: true