CI: update Docker image before we do anything (!731)

This resolves issues like broken Python versions

.gitlab-ci.yml

@@ -8,6 +8,9 @@ stages:
   - first
   - second
 
+.before_script: &before_script
+  - apk -q upgrade
+
 # defaults for "only"
 # We need to run the CI jobs in a "merge request specific context", if CI is
 # running in a merge request. Otherwise the environment variable that holds the
@@ -30,6 +33,7 @@ wiki:
     changes:
       - device/device-*
   before_script:
+    - *before_script
     - apk -q add python3
   script:
     - .gitlab-ci/check_devices_in_wiki.py --booting
@@ -42,6 +46,7 @@ testcases-linting:
     changes:
       - .gitlab-ci/*
   before_script:
+    - *before_script
     - apk -q add py3-flake8
   script:
     - flake8 --ignore E501,F401,E722,W504,W605
@@ -51,6 +56,7 @@ shellcheck:
   stage: first
   <<: *only-default
   before_script:
+    - *before_script
     - apk -q add shellcheck
   script:
     - .gitlab-ci/shellcheck.sh
@@ -60,6 +66,7 @@ aports-static:
   stage: first
   <<: *only-default
   before_script:
+    - *before_script
     - .gitlab-ci/install_pmbootstrap.sh pytest
   script:
     - apk -q add git
@@ -82,6 +89,7 @@ mr-settings:
   only:
     - merge_requests
   before_script:
+    - *before_script
     - apk -q add python3
   script:
     - .gitlab-ci/check_mr_settings.py
@@ -92,6 +100,7 @@ aports-static-upstream:
   only:
     - master@postmarketOS/pmaports
   before_script:
+    - *before_script
     - .gitlab-ci/install_pmbootstrap.sh pytest
   script:
     - su pmos -c ".gitlab-ci/run_testcases.sh
@@ -109,6 +118,7 @@ aports-build:
   stage: second
   <<: *only-default
   before_script:
+    - *before_script
     - .gitlab-ci/install_pmbootstrap.sh git
   script:
     - PYTHONUNBUFFERED=1 su pmos -c ".gitlab-ci/build_changed_aports.py"