v1.7.3

This is a maintenance release of nerves_system_br that continues to use
Buildroot 2019.02.x releases. Buildroot 2019.02 is a "long term support" release
for the Buildroot project and 2019.02.3 is the current latest release. See
https://git.busybox.net/buildroot/plain/CHANGES?id=2019.02.3 for details.

• Package updates
  • Buildroot 2019.02.3
  • Erlang 22.0.2
  • erlinit v1.5.0