Refactor CMakeLists and GitLab CI/CD pipeline

- Remove nested minimum required to supress warnings.
- Declare SystemC as system library to supress warnings in headers.
- Add a BUILD_SHARED_LIBS option
- Remove hardcoded STATIC in various add_library calls to honor the
  BUILD_SHARED_LIBS option
- Remove _deps/ directory from the build directory in GitLab pipeline
- Remove *.tdb files after test stage in pipeline
- Set Ninja as the default generator for the dev preset and re-enable
  colored diagnostics

.gitlab-ci.yml

@@ -14,6 +14,7 @@ build:
     after_script:
         - find . -name "*.o" -type f -delete
         - find . -name "*.a" -type f -delete
+        - rm -r build/coverage/_deps
     artifacts:
         paths:
             - build/coverage
@@ -26,6 +27,8 @@ test:
     script:
         - cd build/coverage
         - ctest --output-on-failure -j$(nproc)
+    after_script:
+        - find . -name "*.tdb" -type f -delete
     artifacts:
         paths:
             - build/coverage