github: check source prep before running gitlab CI

The source preparation script now generates the gitalb-ci.yml and checks
that it's up to date with new image configurations.  Don't run gitlab CI
tests if the source prep check doesn't succeed since it might end up
testing the wrong thing (distros that have been removed, for example).

Also, we need build dependencies to run the script now since it
compiles and runs the list-images command.

Signed-off-by: Achilleas Koutsou <achilleas@koutsou.net>

.github/workflows/gitlab-helper.yml

@@ -1,6 +1,7 @@
-# This workflow runs on PRs and the merge queue and is only responsible for
-# starting the "Start GitLab CI" workflow in a way that makes it possible to
-# use secrets.
+# This workflow runs on PRs and the merge queue and is responsible for starting
+# the "Start GitLab CI" workflow in a way that makes it possible to use
+# secrets. The workflow first runs source preparation to make sure that the
+# gitlab-ci.yml is up to date.
 ---
 name: GitLab
 
@@ -12,6 +13,39 @@ on:
   merge_group:
 
 jobs:
+  prepare:
+    name: "🔍 Check source preparation"
+    runs-on: ubuntu-latest
+    steps:
+
+      - name: Set up Go 1.20
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.20"
+        id: go
+
+      - name: Check out code into the Go module directory
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Install dependencies
+        run: |
+          sudo apt update
+          sudo apt install -y libgpgme-dev libbtrfs-dev libdevmapper-dev
+
+      - name: Check that source has been prepared
+        run: |
+          ./tools/prepare-source.sh
+          if [ -n "$(git status --porcelain)" ]; then
+            echo
+            echo "Please include these changes in your branch: "
+            git status -vv
+            exit "1"
+          else
+            exit "0"
+          fi
+
   gitlab-ci-helper:
     name: "Gitlab CI trigger helper"
     runs-on: ubuntu-latest

.github/workflows/tests.yml

@@ -136,34 +136,6 @@ jobs:
           version: v1.54.2
           args: --verbose --timeout 5m0s
 
-  prepare:
-    name: "🔍 Check source preparation"
-    runs-on: ubuntu-latest
-    steps:
-
-      - name: Set up Go 1.20
-        uses: actions/setup-go@v5
-        with:
-          go-version: "1.20"
-        id: go
-
-      - name: Check out code into the Go module directory
-        uses: actions/checkout@v4
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
-
-      - name: Check that source has been prepared
-        run: |
-          ./tools/prepare-source.sh
-          if [ -n "$(git status --porcelain)" ]; then
-            echo
-            echo "Please include these changes in your branch: "
-            git status -vv
-            exit "1"
-          else
-            exit "0"
-          fi
-
   shellcheck:
     name: "🐚 Shellcheck"
     runs-on: ubuntu-latest