Pullup ticket #6407 - requested by nia
www/firefox: build fix
www/firefox78: build fix

Revisions pulled up:
- www/firefox/mozilla-common.mk                                1.196
- www/firefox78/mozilla-common.mk                              1.8

---
  Module Name: pkgsrc
  Committed By: nia
  Date: Tue Jan 19 22:40:26 UTC 2021

  Modified Files:
  pkgsrc/www/firefox: mozilla-common.mk
  pkgsrc/www/firefox78: mozilla-common.mk

  Log Message:
  firefox(78): set GCC_REQD

(bsiegert)