Attempted to build hostapd using this command on i386 and amd64 FreeBSD11.0Stable 

make __MAKE_CONF=/dev/null -C /usr/ports/net/hostapd -DBATCH -DMAKE_JOBS_UNSAFE clean package

results in

  cc  ../src/ap/ieee802_11_vht.c
  cc  ../src/drivers/driver_common.c
../src/ap/ieee802_11_vht.o: In function `hostapd_eid_txpower_envelope':
../src/ap/ieee802_11_vht.c:(.text+0x309): undefined reference to `hostapd_is_dfs_required'
cc: error: linker command failed with exit code 1 (use -v to see invocation)
gmake[1]: *** [Makefile:1063: hostapd] Error 1
gmake[1]: Leaving directory '/usr/ports/net/hostapd/work/hostapd-2.6/hostapd'
*** Error code 1

The same result obtained when using GCC5 (via ports) or clang4 (base)

Build environment is FreeBSD 11.0-STABLE #0 r317177M: Thu Apr 20 17:08:03 AEST 2017

Unfortunately it looks like it may be a linking problem?

# cd /var/ports/usr/ports/net/hostapd/work && find ./ -type f | xargs grep -i hostapd_eid_txpower_envelope

./hostapd-2.6/src/ap/beacon.c:          pos = hostapd_eid_txpower_envelope(hapd, pos);
./hostapd-2.6/src/ap/beacon.c:          tailpos = hostapd_eid_txpower_envelope(hapd, tailpos);
./hostapd-2.6/src/ap/ieee802_11.h:u8 * hostapd_eid_txpower_envelope(struct hostapd_data *hapd, u8 *eid);
./hostapd-2.6/src/ap/ieee802_11_vht.c:u8 * hostapd_eid_txpower_envelope(struct hostapd_data *hapd, u8 *eid)

Please note: __MAKE_CONF=/dev/null means that there is no /etc/make.conf involved.

And # svnlite info /usr/ports/net/hostapd
Path: /usr/ports/net/hostapd
Working Copy Root Path: /usr/ports
URL: https://svn.freebsd.org/ports/head/net/hostapd
Relative URL: ^/head/net/hostapd
Repository Root: https://svn.freebsd.org/ports
Repository UUID: 35697150-7ecd-e111-bb59-0022644237b5
Revision: 439002
Node Kind: directory
Schedule: normal
Last Changed Author: cy
Last Changed Rev: 437179
Last Changed Date: 2017-03-29 12:49:02 +1100 (Wed, 29 Mar 2017)

Unfortunately I'm able to revert as we only use certs (so the vulnerability that this update addresses is moot), but the problem remains.