recipes-devtools: replace virtclass-native(sdk) with class-native(sdk)

The overrides virtclass-native and virtclass-nativesdk are deprecated,
which should be replaced by class-native and class-nativesdk.

[YOCTO #3297]

(From OE-Core rev: bb67ddeb2eed3e25c626a279ef53a7e8c7bfe6f2)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/flex/flex.inc

@@ -10,6 +10,6 @@ SRC_URI = "${SOURCEFORGE_MIRROR}/flex/flex-${PV}.tar.bz2 "
 
 inherit autotools gettext
 
-do_install_append_virtclass-native() {
+do_install_append_class-native() {
 	create_wrapper ${D}/${bindir}/flex M4=${STAGING_BINDIR_NATIVE}/m4
 }