github: reorganize workflows and add drybuilds

.github/workflows/nix-drybuild.yml

@@ -0,0 +1,53 @@
+name: "nix-drybuild"
+on:
+  push:
+    paths-ignore:
+      - '.github/**'
+      - '_img/**'
+  workflow_dispatch:
+jobs:
+  fallarbor-drybuild:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@main
+        with:
+          fetch-depth: 1
+      - uses: DeterminateSystems/nix-installer-action@main
+      - name: Drybuild fallarbor
+        run: nix build --dry-run .#nixosConfigurations.fallarbor.config.system.build.toplevel
+lavaridge-drybuild:
+  runs-on: ubuntu-latest
+  steps:
+    - uses: actions/checkout@main
+      with:
+        fetch-depth: 1
+    - uses: DeterminateSystems/nix-installer-action@main
+    - name: Drybuild lavaridge
+      run: nix build --dry-run .#nixosConfigurations.lavaridge.config.system.build.toplevel
+mauville-drybuild:
+  runs-on: ubuntu-latest
+  steps:
+    - uses: actions/checkout@main
+      with:
+        fetch-depth: 1
+    - uses: DeterminateSystems/nix-installer-action@main
+    - name: Drybuild mauville
+      run: nix build --dry-run .#nixosConfigurations.mauville.config.system.build.toplevel
+petalburg-drybuild:
+  runs-on: ubuntu-latest
+  steps:
+    - uses: actions/checkout@main
+      with:
+        fetch-depth: 1
+    - uses: DeterminateSystems/nix-installer-action@main
+    - name: Drybuild petalburg
+      run: nix build --dry-run .#nixosConfigurations.petalburg.config.system.build.toplevel
+rustboro-drybuild:
+  runs-on: ubuntu-latest
+  steps:
+    - uses: actions/checkout@main
+      with:
+        fetch-depth: 1
+    - uses: DeterminateSystems/nix-installer-action@main
+    - name: Drybuild rustboro
+      run: nix build --dry-run .#nixosConfigurations.rustboro.config.system.build.toplevel