[ci] Consistent naming.

.gitlab-ci.yml

 stages:
   - pre-checks
-  - test
+  - build
   - checks
   - gui
   - package
@@ -18,8 +18,8 @@ variables:
 include:
   # extends
   - local: '/scripts/ci/extends/defaults.yml'
-  - local: '/scripts/ci/extends/build.yml'
-  - local: '/scripts/ci/extends/build-win.yml'
+  - local: '/scripts/ci/extends/template-build-linux.yml'
+  - local: '/scripts/ci/extends/template-build-win.yml'
   - local: '/scripts/ci/extends/container-maker-setup.yml'
   - local: '/scripts/ci/extends/vs2019-environment.yml'
   - local: '/scripts/ci/extends/test-artifacts.yml'

scripts/ci/extends/build.yml → scripts/ci/extends/template-build-linux.yml

-.build_definition:
-  stage: test
+.template-build-linux:
+  stage: build
   extends:
     - .defaults
     - .test-artifacts

scripts/ci/extends/build-win.yml → scripts/ci/extends/template-build-win.yml

-.build_win_definition:
-  stage: test
+.template-build-win:
+  stage: build
 
   tags:
     - windows

scripts/ci/jobs/build-docs.yml

 build docs:
-  stage: test
+  stage: build
   image:
     name: $CONTAINER_GCC_IMAGE
 

scripts/ci/jobs/build-gui-linux.yml

 build gui linux:
-  extends: .build_definition
+  extends: .template-build-linux
   stage: gui
   when: manual
 

scripts/ci/jobs/build-gui-mac.yml

 build gui mac:
-  extends: .build_definition
+  extends: .template-build-linux
   stage: gui
   tags:
     - mac

scripts/ci/jobs/build-gui-win.yml

 build gui win:
-  extends:
-    - .build_win_definition
+  extends: .template-build-win
   stage: gui
   when: manual
 

scripts/ci/jobs/build-linux.yml

 build linux:
-  extends: .build_definition
+  extends: .template-build-linux
 
   variables:
     BUILD_DIR: "build"

scripts/ci/jobs/build-mac.yml

 build mac:
-  extends: .build_definition
+  extends: .template-build-linux
 
   tags:
     - mac

scripts/ci/jobs/build-win.yml

 build win:
-  extends:
-    - .build_win_definition
+  extends: .template-build-win
 
   variables:
     BUILD_DIR: build-win