archivers/arj: Fix build inside ezjail

For yet unclear reason this port was failing to build inside a jail
built using ezjail. It ended up producing a broken msgbind binary that
crashes early with 'Abort trap' message.

ezjail built jail uses lots of symlinks pointing to a nullfs mounted
partition and this combination seems to be the cause of this issue.

After many tests jsm@ figured out that removing LD_STRIP definition from
gnu/configure script solves the case. There is still something wrong,
maybe on nullfs code, that should be investigated, but at least it fixes
this port build.

PR: 235636
Reported by: Peter Putzer <freebsd@mnd.sc>
Sponsored by: Rubicon Communications, LLC ("Netgate")