Can't build using `CFLAGS="-DCONFIG_DEBUG_SYSLOG -DCONFIG_IEEE80211AC" make`

[Opty]

Hello,

using https://slackbuilds.org/slackbuilds/15.0/network/hostapd/hostapd.defconfig
as .config and `CFLAGS="-DCONFIG_DEBUG_SYSLOG -DCONFIG_IEEE80211AC"
make`, it fails with:

[...]
  CC  ../src/ap/acs.c
/usr/bin/ld: /home/opty/tmp/hostapd-2.10/build/hostapd/src/ap/beacon.o:
in function `hostapd_gen_probe_resp':
beacon.c:(.text+0x10c5): undefined reference to `hostapd_eid_vht_capabilities'
/usr/bin/ld: beacon.c:(.text+0x10d9): undefined reference to
`hostapd_eid_vht_operation'
/usr/bin/ld: beacon.c:(.text+0x116c): undefined reference to
`hostapd_eid_vendor_vht'
/usr/bin/ld: /home/opty/tmp/hostapd-2.10/build/hostapd/src/ap/beacon.o:
in function `ieee802_11_build_ap_params':
beacon.c:(.text+0x29b4): undefined reference to `hostapd_eid_vht_capabilities'
/usr/bin/ld: beacon.c:(.text+0x29c8): undefined reference to
`hostapd_eid_vht_operation'
/usr/bin/ld: beacon.c:(.text+0x2a5b): undefined reference to
`hostapd_eid_vendor_vht'
/usr/bin/ld: /home/opty/tmp/hostapd-2.10/build/hostapd/src/ap/ieee802_11.o:
in function `check_assoc_ies':
ieee802_11.c:(.text+0x5067): undefined reference to `copy_sta_vht_capab'
/usr/bin/ld: ieee802_11.c:(.text+0x5095): undefined reference to
`set_sta_vht_opmode'
/usr/bin/ld: ieee802_11.c:(.text+0x513c): undefined reference to
`copy_sta_vendor_vht'
/usr/bin/ld: /home/opty/tmp/hostapd-2.10/build/hostapd/src/ap/ieee802_11.o:
in function `add_associated_sta':
ieee802_11.c:(.text+0x5ca8): undefined reference to `hostapd_get_vht_capab'
/usr/bin/ld: /home/opty/tmp/hostapd-2.10/build/hostapd/src/ap/ieee802_11.o:
in function `send_assoc_resp':
ieee802_11.c:(.text+0x60f4): undefined reference to
`hostapd_eid_vht_capabilities'
/usr/bin/ld: ieee802_11.c:(.text+0x6108): undefined reference to
`hostapd_eid_vht_operation'
/usr/bin/ld: ieee802_11.c:(.text+0x61b6): undefined reference to
`hostapd_eid_vendor_vht'
collect2: error: ld returned 1 exit status
make: *** [Makefile:1284: hostapd] Error 1

If i enable CONFIG_IEEE80211AC manually in .config, build passes, am I
doing anything wrong? It seems like order/dependency issue.

Regards,
Opty