v1.2.0-rc.0

This release updates gcc from version 7.3.0 to 8.3.0 and includes various
updates to the C runtime. See https://gcc.gnu.org/ for the many changes in the
gcc 8.x releases.

• Tool versions

  • glibc 2.29
  • muslc 1.1.21

• Updated dependencies

  • nerves v1.4
  • nerves_toolchain_ctng v1.6.0