gitlab-ci: Create two different jobs for autotools and meson builds

Signed-off-by: Arnaud Rebillout <arnaud.rebillout@collabora.com>

.gitlab-ci.yml

@@ -1,6 +1,6 @@
 image: registry.freedesktop.org/pulseaudio/pulseaudio/ubuntu:18.04
 
-build:
+build-autotools:
   stage: build
   script:
     - export MAKEFLAGS="-j$(nproc)"
@@ -13,10 +13,17 @@ build:
     - make check-daemon
     - ulimit -c 0 # don't dump core files on tests that are supposed to assert
     - make distcheck
-    - cd ..
-    - meson . build-meson
-    - ninja -C build-meson
   artifacts:
     paths:
       - build/
-      - build-meson/
+
+build-meson:
+  stage: build
+  script:
+    - meson build
+    - cd build
+    - ninja
+    - ninja test
+  artifacts:
+    paths:
+      - build/