Bug#892395: firefox-esr: build-depends on GCC 6

[pochu at debian.org]

Source: firefox-esr
Severity: serious
Tags: sid buster
User: debian-gcc at lists.debian.org
Usertags: gcc-6-rm

Hi,

firefox-esr build-depends on GCC 6. We now have GCC 7 (default) and
GCC 8 in the archive, so please make your package build with a newer
compiler (preferably the default one) again, since we'd like to
remove GCC 6 from testing before the buster release.

Cheers, Emilio