Wrap call to build_fortran_extensions.py script in try/except.
Wrap call to build_fortran_extensions.py script in try/except.

Should not bother calling this script if we cannot find a compiler. This is relevant for building the docs on readthedocs,
or any user who just wants the pure python components.

brian-rose/climlab,cjcardinale/climlab,brian-rose/climlab,cjcardinale/climlab,cjcardinale/climlab