def generate(env):
    """Add Builders and construction variables for g77 to an Environment."""
    add_all_to_env(env)
    add_f77_to_env(env)

    fcomp = env.Detect(compilers) or 'g77'
    if env['PLATFORM'] in ['cygwin', 'win32']:
        env['SHFORTRANFLAGS'] = SCons.Util.CLVar('$FORTRANFLAGS')
        env['SHF77FLAGS'] = SCons.Util.CLVar('$F77FLAGS')
    else:
        env['SHFORTRANFLAGS'] = SCons.Util.CLVar('$FORTRANFLAGS -fPIC')
        env['SHF77FLAGS'] = SCons.Util.CLVar('$F77FLAGS -fPIC')

    env['FORTRAN'] = fcomp
    env['SHFORTRAN'] = '$FORTRAN'

    env['F77'] = fcomp
    env['SHF77'] = '$F77'

    env['INCFORTRANPREFIX'] = "-I"
    env['INCFORTRANSUFFIX'] = ""

    env['INCF77PREFIX'] = "-I"
    env['INCF77SUFFIX'] = ""
Add Builders and construction variables for g77 to an Environment.