CI: Fix OCI image builds with cache mounts

Apt needs exclusive access to its data, so the caches use the option
`sharing=locked`, which will make sure multiple parallel builds using
the same cache mount will wait for each other and not access the same
cache files at the same time. You could also use `sharing=private` if
you prefer to have each build create another cache directory in this
case.

-- moby/buildkit@a577b86201

Author: amotl

Dockerfile

@@ -13,7 +13,9 @@ FROM python:3.11-slim-bullseye
 
 # Install build prerequisites.
 RUN rm -f /etc/apt/apt.conf.d/docker-clean; echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' > /etc/apt/apt.conf.d/keep-cache
-RUN --mount=type=cache,id=apt-cache,target=/var/cache/apt --mount=type=cache,id=apt-lib,target=/var/lib/apt \
+RUN \
+    --mount=type=cache,id=apt,sharing=locked,target=/var/cache/apt \
+    --mount=type=cache,id=apt,sharing=locked,target=/var/lib/apt \
     true \
     && apt-get update \
     && apt-get install --no-install-recommends --no-install-suggests --yes git build-essential librrd-dev

Dockerfile.full

@@ -13,7 +13,9 @@ FROM python:3.11-slim-bullseye
 
 # Install build prerequisites.
 RUN rm -f /etc/apt/apt.conf.d/docker-clean; echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' > /etc/apt/apt.conf.d/keep-cache
-RUN --mount=type=cache,id=apt-cache,target=/var/cache/apt --mount=type=cache,id=apt-lib,target=/var/lib/apt \
+RUN \
+    --mount=type=cache,id=apt,sharing=locked,target=/var/cache/apt \
+    --mount=type=cache,id=apt,sharing=locked,target=/var/lib/apt \
     true \
     && apt-get update \
     && apt-get install --no-install-recommends --no-install-suggests --yes git build-essential librrd-dev