flex,bison: Add nativesdk variants

It is needed in some SDKs that we ship own
version of lex/yacc for sdk host

(From OE-Core rev: 536c9e42d316efb42651fdc2eba1b8548d74329d)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/bison/bison_2.5.1.bb

@@ -33,4 +33,4 @@ do_install_append_virtclass-native() {
 		BISON_PKGDATADIR=${STAGING_DATADIR_NATIVE}/bison
 }
 #bison-native encodes the staging M4 path
-BBCLASSEXTEND = "native"
+BBCLASSEXTEND = "native nativesdk"

meta/recipes-devtools/flex/flex_2.5.35.bb

@@ -2,7 +2,7 @@ require flex.inc
 PR = "r3"
 LICENSE="BSD"
 LIC_FILES_CHKSUM = "file://COPYING;md5=e4742cf92e89040b39486a6219b68067"
-BBCLASSEXTEND = "native"
+BBCLASSEXTEND = "native nativesdk"
 
 SRC_URI += "file://avoid-FORTIFY-warnings.patch \
             file://int-is-not-the-same-size-as-size_t.patch"