Remove the temporary mountpoint on exit
bemerge
does not remove the temporary mountpoint, so a lot of them remain after using it a few times.
# bemerge -b gentoo-7 -- true
'gentoo-7' mounted successfully on: '/tmp/tmp.bAQmoS'.
'gentoo-7' unmounted successfully.
# ls -1d /tmp/tmp.*
/tmp/tmp.bAQmoS
# bemerge -b gentoo-7 -- true
'gentoo-7' mounted successfully on: '/tmp/tmp.Pr9hMe'.
'gentoo-7' unmounted successfully.
# ls -1d /tmp/tmp.*
/tmp/tmp.bAQmoS
/tmp/tmp.Pr9hMe