Incorporate review suggestions

* Reorder keywords in CI jobs and put extends keyword first.
* Use Python 3.10 as default base image.
* Use full path to executable of exercise app when calling app.

.gitlab-ci.yml

@@ -12,7 +12,7 @@ stages:
   - run
 
 default:
-  image: python:3.9
+  image: python:3.10
 
 .install_dependencies:
   before_script:
@@ -41,11 +41,11 @@ lint:
     - cpplint --recursive src/ tests/
 
 build:gcc:
-  image: gcc:${VERSION}
-  stage: build
   extends:
     - .install_dependencies
     - .compiler_versions
+  image: gcc:${VERSION}
+  stage: build
   script:
     - cmake -S . -B build_gcc_${VERSION}
     - cmake --build build_gcc_${VERSION}
@@ -54,11 +54,11 @@ build:gcc:
       - build_gcc_${VERSION}
 
 test:gcc:
-  image: gcc:${VERSION}
-  stage: test
   extends:
     - .install_dependencies
     - .compiler_versions
+  image: gcc:${VERSION}
+  stage: test
   script:
     - cd build_gcc_${VERSION} && ctest
   dependencies:
@@ -68,7 +68,7 @@ run:
   image: gcc:11
   stage: run
   script:
-    - cd build_gcc_11/bin/ && ./helloWorld
+    - ./build_gcc_11/bin/helloWorld
   dependencies:
     - "build:gcc"