'The \'-V\' option works for nag compilers.
Output looks like this::
NAG Fortran Compiler Release 6.0(Hibiya) Build 1037
Product NPL6A60NA for x86-64 Linux'

@classmethod
def default_version(self, comp):

    return get_compiler_version(comp, '-V', 'NAG    Fortran    Compiler    Release    ([0-9.]+)')
