ci: Add new argument to apk

Breaking the CI is definitely one way to make me care about your
platform, Alpine.

.github/workflows/alpine-gcc-latest.yml

@@ -17,7 +17,7 @@ jobs:
     - uses: actions/checkout@v2
     - name: set up environment
       run: |
-        apk add gcc musl-dev gobject-introspection gtk-doc glib py3-wheel py3-setuptools ninja py3-pip
+        apk --break-system-packages add gcc musl-dev gobject-introspection gtk-doc glib py3-wheel py3-setuptools ninja py3-pip
         pip install meson==0.55.3
 
     - name: default build