return code should reflect whether install worked or not

[dch]

while testing the known issue of cross-device link handling, I noticed that
a failed pkg run still returns 0, even though FreeBSD-runtime didn't
succeed, and 43 packages were not installed.

...
[239/283] Extracting FreeBSD-resolvconf-man-15.snap20241026125659: 100%
[240/283] Installing FreeBSD-runtime-15.snap20250606013602...
[240/283] Extracting FreeBSD-runtime-15.snap20250606013602:  32%
pkg: Fail to create hardlink: /.pkgtemp..profile.CNoXJiaVh9G3 <-> /root/.pkgtemp..profile.zltb4Tr3AL9Q:Cross-device link
[240/283] Extracting FreeBSD-runtime-15.snap20250606013602: 100%
Error: exit
Merged /etc/pkg/FreeBSD.conf
Merged /etc/rc.d/nuageinit
Merged /etc/mtree/BSD.root.dist
Merged /etc/blacklistd.conf
Restarting sshd
Performing sanity check on sshd configuration.
Stopping sshd.
Waiting for PIDS: 65097.
Performing sanity check on sshd configuration.
Starting sshd.
root@akai ~# echo $status
0