CI: easier yaml anchor

.gitlab-ci.yml

 .build_and_test_template: &build_and_test_definition
-  script:
-    - mkdir -pv build
-    - cd build
-    - cmake -DCMAKE_BUILD_TYPE=release -DBUILD_DEMOS=ON -DBUILD_TESTS=ON ..
-    - make -j$(nproc)
-    - ctest -j$(nproc)
-    # run demos
-    - ../bin/hello_wolf
-    - ../bin/hello_wolf_autoconf
-    - make install
+  - mkdir -pv build
+  - cd build
+  - cmake -DCMAKE_BUILD_TYPE=release -DBUILD_DEMOS=ON -DBUILD_TESTS=ON ..
+  - make -j$(nproc)
+  - ctest -j$(nproc)
+  # run demos
+  - ../bin/hello_wolf
+  - ../bin/hello_wolf_autoconf
+  - make install
 
 build_and_test:xenial:
   image: labrobotica/wolf_deps:16.04
   except:
     - master
-  <<: *build_and_test_definition
+  script:
+    - *build_and_test_definition
 
 build_and_test:bionic:
   image: labrobotica/wolf_deps:18.04
   except:
     - master
-  <<: *build_and_test_definition
+  script:
\ No newline at end of file
+    - *build_and_test_definition
\ No newline at end of file