trying to improve online docs rendering

.gitlab-ci.yml

-image: python:alpine
+image: ubuntu:21.04
 
 test:
   stage: test
   script:
-  - apk add --no-cache build-base gcc abuild binutils cmake cmake-doc extra-cmake-modules extra-cmake-modules-doc py3-pip python3 python3-dev
+  - apt-get install build_essential gcc cmake python3-pip python3 python3-dev
   - pip install -U -r requirements.txt
   - python setup.py install
   - sphinx-build -b html docs/source public
@@ -15,7 +15,7 @@ test:
 pages:
   stage: deploy
   script:
-  - apk add --no-cache build-base gcc abuild binutils cmake cmake-doc extra-cmake-modules extra-cmake-modules-doc py3-pip python3 python3-dev
+  - apt-get install build_essential gcc cmake python3-pip python3 python3-dev
   - pip install -U -r requirements.txt
   - python setup.py install
   - sphinx-build -b html docs/source public