Since zephyr commit zephyrproject-rtos/zephyr@9fc99928caf04c3ae78 and zephyrproject-rtos/zephyr@49d0ad55206aa, the Zephyr main branch is not compatible with the Zephyr SDK 0.15.x anymore, it now requires 0.16.x. The Zephyr main branch now depends on different (and correct) toolchain names which are not present in 0.15.x

-> this requires some "infrastructure" updates

Every PR trying to build the Zephyr main branch (a.k.a. "zmain") started to fail like this, example in https://github.com/thesofproject/sof/actions/runs/4984592530

CMake Error at /zep_workspace/zephyr/cmake/compiler/gcc/target.cmake:12 (message):
  C compiler
  /home/cwd_user/zephyr-sdk-0.15.2/xtensa-intel_ace15_mtpm_zephyr-elf/bin/xtensa-intel_ace15_mtpm_zephyr-elf-gcc
  not found - Please check your toolchain installation

• Fixing this for Linux compilation should be more or less a one-line change in the zephyr/docker-run.sh script (example in previous commit 11441d8)

• Change ubuntu-20.04 -> ubuntu-22.04 in the 2 files .github/workflows/*zephyr.yml to stay in sync with https://github.com/zephyrproject-rtos/docker-image/pkgs/container/zephyr-build

• The Windows compilation that we've enjoyed thanks to @aborisovich's heroic work (commit df1ba22) is unfortunately a bit more complicated.

Note upgrading will also help with OpenSSL 1.x removal where this has already been discussed:

• [RFC] Remove OpenSSL 1.x support rimage#157