NetCDF is unreliable on Macs with debug/shared lib builds

[pbtoast]

NetCDF tests that write to files all seem to fail when polyglot is built against a version of polymec with shared=1 and debug=1, reporting "HDF errors." The attached test log shows the nature of these errors.
LastTest.txt

[pbtoast]

For now, I'm just removing this configuration from the test matrix, since this is likely an issue in the NetCDF library.