Adjust CI to new purpose-built container image

.gitlab-ci.yml

 variables:
   GIT_SUBMODULE_STRATEGY: normal
 
-sagetex-sty-copy:
-  image: 
-    name: docker.io/sagemath/sagemath
-    entrypoint: [""]
-  tags: ["x64"]
-  script: cp /home/sage/sage/local/var/lib/sage/venv-python3.*/share/texmf/tex/latex/sagetex/sagetex.sty .
-  artifacts:
-    paths:
-      - sagetex.sty
-
-create-sage-scripts:
-  image: docker.io/texlive/texlive
-  tags: ["x64"]
-  needs: [sagetex-sty-copy]
-  script:
-    - make main.sagetex.sage
-    - make filtered_sage.txt
-  after_script:
-    - cat main.log
-  artifacts:
-    paths:
-      - "*"
-
-run-sage-script:
-  image: 
-    name: docker.io/sagemath/sagemath
-    entrypoint: [""]
-  needs: [create-sage-scripts]
-  tags: ["x64"]
-  script:
-    - sage -pip install "pseudowalls==0.0.3" --extra-index-url https://gitlab.com/api/v4/projects/43962374/packages/pypi/simple
-    -  sage main.sagetex.sage
-  artifacts:
-    paths:
-      - "*"
-
 build:
-  image: docker.io/texlive/texlive
-  needs: [run-sage-script]
+  image: registry.gitlab.com/lukenaylor/latex/sagetex-image:latest
   tags: ["x64"]
   script:
-    - latexmk || echo failed final latexmk
+    - sage -pip install "pseudowalls==0.0.3" --extra-index-url https://gitlab.com/api/v4/projects/43962374/packages/pypi/simple
+    - make || echo make failed
   artifacts:
     paths:
       - "*"