if MPSD_MICROARCH is not defined, use archspec to determine

What does the MR provide?

• 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).

tests.py

@@ -324,6 +324,6 @@ def test_interface(tmp_path):
     # check that the help message is printed when -h is provided
     # check that the error messages are also logged to the log file
 
+
 # other tests to add (ideally)
 # - get_native_microarchitecture()
-