Attempting to cross-compile Firefox will be rather challenging. It has
loads of dependencies, written in a variety of languages. Some issues
are more interesting than others. Notably, _dev-libs/nss_ needs to be
installed on the host in order to cross-compile itself, but its ebuild
does not specify this ([Bug 759127][0]). Also the build system for
_gnome-base/librsvg_ is broken: [Gentoo Bug 835758][1], [GNOME
Issue #810][2]. Cross-compiling _dev-libs/gobject-introspection_ is
also broken ([Bug 759127][3], [850895][4]).
With all of these changes, we can get to the point where Portage starts
building Firefox, it will take hours and all of my machine's resources,
so I haven't tested if will actually build. We shall see once Jenkins
tries it...
[0]: https://bugs.gentoo.org/759127
[1]: https://bugs.gentoo.org/835758
[2]: https://gitlab.gnome.org/GNOME/librsvg/-/issues/810
[3]: https://bugs.gentoo.org/850895
[4]: https://bugs.gentoo.org/751325
We need the Broadcom firmware from the _linux-firmware_ package (and
nothing else). We also need _wpa_supplicant_, to configure the WiFi
connection. Finally, we need to configure _systemd-networkd_ to manage
the network device.
Dustin