C compiler ignores environment variables set in python

[pkienzle]

The choice of C compiler and DLL path in sasmodels/kerneldll.py is set when the module is loaded, not when the compiler is first used. This means that setting the SAS_COMPILER environment variable with os.environ["SAS_COMPILER"] will have no effect if sasmodels.kerneldll has already been imported.

The upshot is that you can't use -DSAS_COMPILER=msvc on the sascomp command line to force the use of the MSVC compiler in windows.

Could delay the selection of compiler until it is first needed or check the environment variables each time.