net/openmpi fails to buid with default options

hello, here's the situation.

fresh install of FreeBSD 10.3 (amd64). I log in for the first time, bring the system up to date ( freebsd-update fetch && freebsd-update install), update the ports tree (
portsnap fetch && portsnap extract

then I try to install net/openmpi with the default options hitting make install clean BATCH=yes

problem is the process hangs forever (=hours) building the slurm mans; here's the last relevant terminal output snippet:

Making all in man1
gmake[6]: Entering directory '/usr/ports/sysutils/slurm-wlm/work/slurm-15.08.12/doc/man/man1'
`dirname sacct.1`/../ 15.08 ./../../html/header.txt ./../../html/footer.txt sacct.1
`dirname sacctmgr.1`/../ 15.08 ./../../html/header.txt ./../../html/footer.txt sacctmgr.1
>>>>>>> sacctmgr.mhtml
('Converting', 'sacctmgr.mhtml', '->', 'sacctmgr.html')


`dirname sview.1`/../ 15.08 ./../../html/header.txt ./../../html/footer.txt sview.1
>>>>>>> sview.mhtml
('Converting', 'sview.mhtml', '->', 'sview.html')

Any hints?
Thank you :)