If MPSD_MICROARCH is not defined as a environment variable, then use archspec to determine it.
if archspec is not available, ask user to provide it via error message and stop.
Where does this matter?
script creates a folder for the microarchitecture.
Found in Docker container that this would be dev-23a/UNKNOWN_MICROARCH/
the same will happen on other user machines (unless they are the Linux laptops provided by MPSD; but we know several people who prefer to run their own distribution, or even non-linux system (i.e. Mac).
