Remove unneeded cached files from appstream

These files cause an untracable difference for the reproducible Bookworm
images, but because they are not needed, they can be removed.

examples/hooks/reproducible/8520-cleanup-appstream-cache.hook.chroot

@@ -0,0 +1,41 @@
+#!/bin/sh
+set -e
+
+# 'appstreamcli refresh --source=os' which is invoked by 'apt-get update'
+# creates cache files that will be re-generated by live-config.
+# These cache files are generated by lb for the C locale, while after boot in
+# the live image the actual language is used (default=en_US) when a network
+# connection was made. If no network is available 'GNOME Software' still works
+# correctly without these cache files.
+# Therefore these files can safely be removed from the live image.
+#
+# However, after all hooks have run, 'apt-get update' is run once again by
+# 'chroot_archives chroot remove', therefore the original executable
+# 'appstreamcli' is moved away by this script, to be restored upon the next
+# invocation.
+
+# Don't run if AppStream is not installed
+if [ ! -e /usr/bin/appstreamcli ];
+then
+  exit 0
+fi
+
+# Don't run if the version of appstream is too old
+if dpkg --compare-versions $(dpkg-query --show --showformat '${Version}\n' appstream | head -1) lt 0.15.2~;
+then
+  exit 0
+fi
+
+# Create a wrapper that restores itself on the next invocation
+mv /usr/bin/appstreamcli /usr/bin/appstreamcli.orig
+cat << EOF > /usr/bin/appstreamcli
+#!/bin/sh
+/usr/bin/appstreamcli.orig \$@
+rm /usr/bin/appstreamcli
+mv /usr/bin/appstreamcli.orig /usr/bin/appstreamcli
+# Delete the cache files
+rm -f /var/cache/swcatalog/cache/C-*.xb
+EOF
+chmod a+x /usr/bin/appstreamcli
+
+echo "P: $(basename $0) Reproducible hook has been applied"