Add check for ReadWritePaths -- exists at SytemD only after version 231

[0bi-w6n-K3nobi]

I just create a new installation for CentOS 7 at LXC container [not LXD].
After running, I found several warning messages with this format:

[/run/systemd/.../.../zzz-lxc-service.conf:6] Unknown lvalue 'ReadWritePaths' in section 'Service'

I did check at Git source from SystemD, and found at NEWS file, that statement ReadWritePaths exist only after version 231.
I rechecked at versions, and get the same conclusion.
Well, ... CentOS 7 has SystemD 219.

Hummm... Looking at DistroBuilder sources, I think just apply the follow patch that will be solve:

--- a/distrobuilder/main.go     2022-04-21 08:38:08.000000000 +0000
+++ b/distrobuilder/main.go     2022-04-22 16:59:30.073944330 +0000
@@ -658,7 +658,7 @@
                        echo "PrivateTmp=no";
                        [ "${systemd_version}" -ge 244 ] && echo "ProtectKernelLogs=no";
                        [ "${systemd_version}" -ge 232 ] && echo "ProtectKernelModules=no";
-                       echo "ReadWritePaths=";
+                       [ "${systemd_version}" -ge 231 ] && echo "ReadWritePaths=";
                fi
        } > "${dropin_dir}/zzz-lxc-service.conf"
 }

I hope I may have helped.

[0bi-w6n-K3nobi]

PS:

Well... yet I had problem after apply this patch.
This is will produce the following error after first zzz-lxc-service.conf generated:

/etc/systemd/system-generators/lxc failed with error code 1.

I did try debug, but simply can't get found why.
If you have idea about this you be free to get another solution.
Therefore, for solve I included the echo ""; not important line, then the final patch will be:

--- a/distrobuilder/main.go     2022-04-21 08:38:08.000000000 +0000
+++ b/distrobuilder/main.go     2022-04-22 16:59:30.073944330 +0000
@@ -658,7 +658,8 @@
                        echo "PrivateTmp=no";
                        [ "${systemd_version}" -ge 244 ] && echo "ProtectKernelLogs=no";
                        [ "${systemd_version}" -ge 232 ] && echo "ProtectKernelModules=no";
-                       echo "ReadWritePaths=";
+                       [ "${systemd_version}" -ge 231 ] && echo "ReadWritePaths=";
+                       echo "";
                fi
        } > "${dropin_dir}/zzz-lxc-service.conf"