def METHOD_NAME(env) -> None:
    """Add Builders and construction variables for cyglink to an Environment."""
    gnulink.METHOD_NAME(env)
    env['LINKFLAGS'] = CLVar('-Wl,-no-undefined')
    env['SHLIBPREFIX'] = 'cyg'
    env['SHLIBSUFFIX'] = '.dll'
    env['IMPLIBPREFIX'] = 'lib'
    env['IMPLIBSUFFIX'] = '.dll.a'
    # Variables used by versioned shared libraries
    # SHLIBVERSIONFLAGS and LDMODULEVERSIONFLAGS are same as in gnulink...
    env['_SHLIBVERSIONFLAGS'] = '$SHLIBVERSIONFLAGS'
    env['_LDMODULEVERSIONFLAGS'] = '$LDMODULEVERSIONFLAGS'
    env['_IMPLIB_PRE_SOURCES'] = _implib_pre_flags
    env['_IMPLIB_POST_SOURCES'] = _implib_post_flags
    env['SHLINKCOM'] = '$SHLINK -o $TARGET $SHLINKFLAGS $__SHLIBVERSIONFLAGS $__RPATH ' \
                       '$_IMPLIB_PRE_SOURCES $SOURCES  $_IMPLIB_POST_SOURCES $_LIBDIRFLAGS $_LIBFLAGS'
    env['LDMODULECOM'] = '$LDMODULE -o $TARGET $SHLINKFLAGS $__LDMODULEVERSIONFLAGS $__RPATH ' \
                         '$_IMPLIB_PRE_SOURCES $SOURCES $_IMPLIB_POST_SOURCES $_LIBDIRFLAGS  $_LIBFLAGS'
    # Overwrite emitters. Cyglink does things differently when creating symlinks
    env['SHLIBEMITTER'] = [cyglink_lib_emitter, cyglink_shlib_symlink_emitter]
    env['LDMODULEEMITTER'] = [cyglink_ldmodule_emitter, cyglink_ldmod_symlink_emitter]
    # This is the non versioned shlib filename
    # If SHLIBVERSION is defined then this will symlink to $SHLIBNAME
    env['SHLIB_NOVERSION_SYMLINK'] = '${IMPLIBPREFIX}$_get_shlib_stem${IMPLIBSUFFIX}'
    env['LDMODULE_NOVERSION_SYMLINK'] = '${IMPLIBPREFIX}$_get_ldmodule_stem${IMPLIBSUFFIX}'
    env['SHLIB_IMPLIBNAME'] = '${IMPLIBPREFIX}$_get_shlib_stem${_SHLIB_IMPLIBSUFFIX}'
    env['LDMODULE_IMPLIBNAME'] = '${IMPLIBPREFIX}$_get_ldmodule_stem${_LDMODULE_IMPLIBSUFFIX}'
    env['_cyglink_shlibversion'] = cyglink_shlibversion
    env['_SHLIB_IMPLIBSUFFIX'] = '${_cyglink_shlibversion}${IMPLIBSUFFIX}'
    env['_SHLIBSUFFIX'] = '${_cyglink_shlibversion}${SHLIBSUFFIX}'
    env['_cyglink_ldmodule_version'] = cyglink_ldmodule_version
    env['_LDMODULESUFFIX'] = '${_cyglink_ldmodule_version}${LDMODULESUFFIX}'
    env['_LDMODULE_IMPLIBSUFFIX'] = '${_cyglink_ldmodule_version}${IMPLIBSUFFIX}'
    # Remove variables set by default initialization which aren't needed/used by cyglink
    # these variables were set by gnulink but are not used in cyglink
    for rv in ['_SHLIBSONAME', '_LDMODULESONAME']:
        if rv in env:
            del env[rv]