fix: forgejo-runner-service.sh config.yml must point to the cache

It is not the default $HOME/.cache/actcache and must be set in
config.yml otherwise it won't be used.

.forgejo/workflows/example-lxc-systemd.yml

@@ -82,6 +82,10 @@ jobs:
            service=/etc/systemd/system/forgejo-runner@.service
            cat $service
 
+           cache=/var/lib/forgejo-runner/runner-$INPUTS_SERIAL-lxc/.cache/actcache
+           touch $cache/something
+           lxc-attach runner-$INPUTS_SERIAL-lxc -- test -f $cache/something
+
        - name: forgejo-runner-service.sh start / stop
          run: |
            set -x

examples/lxc-systemd/forgejo-runner-service.sh

@@ -207,6 +207,11 @@ function ensure_configuration_and_registration() {
 .runner.labels = ["docker:docker://data.forgejo.org/oci/node:${NODEJS_VERSION}-${DEBIAN_RELEASE}","lxc:lxc://debian:${DEBIAN_RELEASE}"]
 EOF
     yq --inplace --from-file $TMPDIR/edit-config $etc/config.yml
+    cat >$TMPDIR/edit-config <<EOF
+.cache.dir = "/var/lib/forgejo-runner/runner-${INPUTS_SERIAL}-lxc/.cache/actcache"
+EOF
+    yq --inplace --from-file $TMPDIR/edit-config $etc/config.yml
+
   fi
 
   if ! test -f $etc/env; then