test: ensure journal dir is writable by container in TEST-13-NSPAWN

The systemd-journal group is not mapped, so ensure the test directory
is owned by root:root so that the mapping works.

Follow-up for 88fce090263ba8944cf491346eae2e8022dfd88d

shell-completion/bash/journalctl

@@ -46,7 +46,8 @@ _journalctl() {
                       --version --list-catalog --update-catalog --list-boots
                       --show-cursor --dmesg -k --pager-end -e -r --reverse
                       --utc -x --catalog --no-full --force --dump-catalog
-                      --flush --rotate --sync --no-hostname -N --fields
+                      --flush --rotate --sync --relinquish-var
+                      --smart-relinquish-var --no-hostname -N --fields
                       --list-namespaces --list-invocations -I -v --verbose'
         [ARG]='-b --boot -D --directory -i --file -F --field -t --identifier
                       -T --exclude-identifier --facility -M --machine -o --output

src/dissect/dissect.c

@@ -6,6 +6,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/file.h>
+#include <unistd.h>
 
 #include "sd-device.h"
 

test/units/TEST-13-NSPAWN.nspawn.sh

@@ -1454,20 +1454,21 @@ testcase_link_journal_host() {
 
     systemd-id128 new > "$root"/etc/machine-id
 
-    mkdir -p /var/log/journal
-
-    hoge="/var/log/journal/$(cat "$root"/etc/machine-id)/hoge"
+    hoge="/var/log/journal/$(cat "$root"/etc/machine-id)/"
+    mkdir -p "$hoge"
+    # The systemd-journal group is not mapped, so ensure the directory is owned by root:root
+    chown root:root "$hoge"
 
     for i in no yes pick; do
         systemd-nspawn \
             --directory="$root" --private-users="$i" --link-journal=host \
             bash -xec 'p="/var/log/journal/$(cat /etc/machine-id)"; mountpoint "$p"; [[ "$(stat "$p" --format=%u)" == 0 ]]; touch "$p/hoge"'
 
-        [[ "$(stat "$hoge" --format=%u)" == 0 ]]
-        rm "$hoge"
+        [[ "$(stat "${hoge}/hoge" --format=%u)" == 0 ]]
+        rm "${hoge}/hoge"
     done
 
-    rm -fr "$root"
+    rm -fr "$root" "$hoge"
 }
 
 testcase_cap_net_bind_service() {