CI: Use 'needs' to make dependencies more clear

GitLab CI has two execution scheduling models. The original model is to
split jobs into stages; jobs within a single stage may execute in
parallel, but execution is serialised between stages.

As we move to supporting multiple OSes and architectures, there is no
need to serialise, e.g. the AArch64 Linux build against the x86-64
FreeBSD container preparation.

Declare our dependencies explicitly using `needs`.

Signed-off-by: Daniel Stone <daniels@collabora.com>

.gitlab-ci.yml

@@ -180,6 +180,9 @@ x86_64-debian-container_prep:
     - .debian-x86_64
     - .fdo.suffixed-image@debian
     - .build-env
+  needs:
+    - job: x86_64-debian-container_prep
+      artifacts: false
 
 .test-env-debian-x86_64:
   tags:
@@ -187,9 +190,13 @@ x86_64-debian-container_prep:
   extends:
     - .build-env-debian-x86_64
     - .build-and-test
+  needs:
+    - job: x86_64-debian-container_prep
+      artifacts: false
 
 # Full build, used for testing under KVM.
 x86_64-debian-full-build:
+  extends: .test-env-debian-x86_64
   variables:
     MESON_OPTIONS: >
       -Doptimization=0
@@ -197,7 +204,6 @@ x86_64-debian-full-build:
       -Dwerror=true
       -Dtest-skip-is-failure=true
       -Dlauncher-libseat=true
-  extends: .test-env-debian-x86_64
   after_script:
   - ninja -C "$BUILDDIR" coverage-html > "$BUILDDIR/meson-logs/ninja-coverage-html.txt"
   - ninja -C "$BUILDDIR" coverage-xml
@@ -219,6 +225,7 @@ docs-build:
 
 # Building without gl-renderer, to make sure this keeps working.
 x86_64-debian-no-gl-build:
+  extends: .test-env-debian-x86_64
   variables:
     MESON_OPTIONS: >
       -Dsimple-clients=damage,im,shm,touch,dmabuf-v4l
@@ -227,7 +234,6 @@ x86_64-debian-no-gl-build:
       -Dpipewire=false
       -Dwerror=true
       -Dlauncher-libseat=true
-  extends: .test-env-debian-x86_64
 
 # Expose docs and coverage reports, so we can show users any changes to these
 # inside their merge requests, letting us check them before merge.
@@ -242,6 +248,11 @@ docs-and-coverage:
     - .debian-x86_64
     - .fdo.suffixed-image@debian
   stage: pages
+  needs:
+    - job: docs-build
+      artifacts: true
+    - job: x86_64-debian-full-build
+      artifacts: true
   timeout: 5m
   script:
   - mv prefix-weston-docs-build/share/doc/weston Documentation
@@ -250,9 +261,6 @@ docs-and-coverage:
   - cp doc/style/lcov-style.css Test_Coverage/gcov.css
   - cp doc/style/*.png Test_Coverage/
   - rm -rf build-* prefix-*
-  dependencies:
-    - docs-build
-    - x86_64-debian-full-build
   artifacts:
     expose_as: 'Documentation preview and test coverage report'
     paths:
@@ -270,8 +278,9 @@ pages:
     - .fdo.suffixed-image@debian
   stage: pages
   timeout: 5m
-  dependencies:
+  needs:
-    - docs-build
+    - job: docs-build
+      artifacts: true
   script:
   - export PREFIX=$(pwd)/prefix-weston-docs-build
   - mkdir public