www/firefox on RPI2: error: instruction requires: armv6t2

[bob prohaska]

With freebsd at 
FreeBSD www.zefox.com 12.0-CURRENT FreeBSD 12.0-CURRENT #50 r318138: Wed May 10 10:30:51 PDT 2017     bob at www.zefox.com:/usr/obj/usr/src/sys/RPI2  arm

ports at 
Revision: 440570

and using 
root at www:/usr/ports/www/firefox # make CFLAGS='-mcpu=cortex-a7' -DBATCH > make.log &

the compilation seems to halt with
/usr/ports/www/firefox/work/firefox-53.0.2/media/webrtc/trunk/webrtc/common_audio/signal_processing/filter_ar_fast_q12_armv7.S:88:3: error: instruction requires: armv6t2
  sbfx r11, r6, #12, #16
  ^
/usr/ports/www/firefox/work/firefox-53.0.2/media/webrtc/trunk/webrtc/common_audio/signal_processing/filter_ar_fast_q12_armv7.S:99:3: error: instruction requires: armv6t2
  sbfx r11, r6, #12, #16
  ^
/usr/ports/www/firefox/work/firefox-53.0.2/media/webrtc/trunk/webrtc/common_audio/signal_processing/filter_ar_fast_q12_armv7.S:142:3: error: instruction requires: armv6t2
  sbfx r8, r6, #12, #16
  ^
gmake[6]: *** [/usr/ports/www/firefox/work/firefox-53.0.2/config/rules.mk:989: filter_ar_fast_q12_armv7.o] Error 1

I'm told this is likely caused by  CFLAGS='-mcpu=cortex-a7', which is
needed to avoid a "NEON not enabled" error earlier in the compile.

Would a bug report be redundant? 

Thanks for reading,

bob prohaska