v1.13.1

The main change in this release is to bump the Linux kernel to 5.4. This follows
the kernel update in the Raspberry Pi OS.

If you have based a custom system off of this one, please inspect the
nerves_defconfig for WiFi firmware changes. WiFi firmware is no longer being
pulled from the rpi-wifi-firmware since that package is out of date.

• Updated dependencies

  • nerves_system_br: bump to v1.13.4
  • Erlang/OTP 23.1.4
  • boardid 1.10.0

• Improvements

  • Enabled reproducible builds in Buildroot to remove some timestamp and build
    path differences in firmware images. This helps delta firmware updates.
  • The memory cgroup controller is no longer enabled by default. This was an
    upstream change. As a result, the memory cgroup directory is no longer
    mounted.