[Sound-open-firmware] change in west usage for SOF Zephyr builds

[Kai Vehmanen]

Hi,

just a heads up that the recent change to 
sof/scripts/xtensa-build-zephyr.py in commit
"xtensa-build-zephyr.py: use west manifest", merged to
SOF main yesterday, has been causing trouble to some users.

The change adds a west manifest to SOF repository. This is
now used to check out zephyr in a specific place in the work
area, and most importantly, to have a version controlled way
to specify which version of Zephyr (and other subprojects) to build
against, when building SOF with Zephyr.

Easiest way to recover is to check out a new work area to
build SOF with Zephyr.

Br, Kai