Add NetBSD/aarch64eb support to */config.guess for self-building and mknative.

XXX
Instead of patching each file, it would be better to maintain single
config.*'s as done in pkgsrc...

Patch provided by ryo@.
OK mrg@.

external/apache2/llvm/autoconf/autoconf/config.guess

@@ -158,6 +158,7 @@ case "${UNAME_MACHINE}:${UNAME_SYSTEM}:${UNAME_RELEASE}:${UNAME_VERSION}" in
 	UNAME_MACHINE_ARCH=`(/sbin/$sysctl 2>/dev/null || \
 	    /usr/sbin/$sysctl 2>/dev/null || echo unknown)`
 	case "${UNAME_MACHINE_ARCH}" in
+	    aarch64eb) machine=aarch64_be-unknown ;;
 	    armeb) machine=armeb-unknown ;;
 	    arm*) machine=arm-unknown ;;
 	    sh3el) machine=shl-unknown ;;