ci: Wait for 'check-commit-log' before continuing

The check-commit-log is quick, and to get a result early is helpful as
one can then more quickly check for failures via the report provided via
the JUnit report.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1491>

.gitlab-ci.yml

@@ -25,8 +25,7 @@ check_commit_log:
         GIT_DEPTH: "100"
     script:
         - ./.gitlab-ci/check-commit-log.sh
-    only:
-        - merge_requests
+    <<: *only_default
     artifacts:
         expire_in: 1 week
         paths:
@@ -90,7 +89,7 @@ no_template_check:
 build:
     image: registry.gitlab.gnome.org/gnome/mutter/master:v4
     stage: build
-    needs: []
+    needs: ["check_commit_log"]
     before_script:
         - .gitlab-ci/checkout-mutter.sh
         - meson mutter mutter/build --prefix=/usr -Dtests=false
@@ -126,7 +125,7 @@ test:
 
 flatpak:
     stage: build
-    needs: []
+    needs: ["check_commit_log"]
     variables:
         SUBPROJECT: "subprojects/extensions-app"
         # Your manifest path

.gitlab-ci/check-commit-log.sh

@@ -1,8 +1,8 @@
 #!/usr/bin/env bash
 
 if [ -z "$CI_MERGE_REQUEST_TARGET_BRANCH_NAME" ]; then
-  echo Cannot review non-merge request
-  exit 1
+  echo This is not a merge request, skipping
+  exit 0
 fi
 
 git fetch $CI_MERGE_REQUEST_PROJECT_URL.git $CI_MERGE_REQUEST_TARGET_BRANCH_NAME