v1.5.0

This release bumps the Linux kernel to 4.19.25. This change had an impact on how
the WiFi regulatory database gets loaded into the kernel. Instead of building it
into the kernel as previously done, the kernel loads it on demand. This requires
that all WiFi drivers be built as kernel modules so that the database isn't
loaded before the root filesystem is mounted. If you made a custom system and
see boot errors about not being able to load the regulatory database, this is
the problem.

• Bux fixes
  • Add TAR option --no-same-owner to fix errors when untarring artifacts as
    the root user.
• Updated dependencies
  • nerves_system_br v1.7.2
  • Linux 4.19.25 with patches from the Raspberry Pi Foundation
• Improvements
  • Bump C compiler options to -O2 from -Os. This provides a small, but
    measurable performance improvement (500ms at boot in a trivial project
    tested on nerves_system_rpi0)