adjust for GCC 4.9 and newer, with mksh R50 and newer

package/mksh/Makefile

@@ -42,7 +42,7 @@ mksh-hostinstall:
 do-build:
 	cd ${WRKBUILD} && CC='${TARGET_CC}' CFLAGS='${TARGET_CFLAGS}' \
 	    CPPFLAGS='${TARGET_CPPFLAGS}' LDFLAGS='${TARGET_LDFLAGS}' \
-	    HAVE_CAN_FSTACKPROTECTORALL=0 \
+	    HAVE_CAN_FSTACKPROTECTORALL=0 HAVE_CAN_FSTACKPROTECTORSTRONG=0 \
 	    TARGET_OS=Linux ${BASH} ${WRKSRC}/Build.sh -Q -r -c lto
 
 mksh-install: