Add an initial miniroot with bootaa64.efi on fat and bsd.rd on ffs.

src/etc/etc.arm64/Makefile.inc

@@ -1,6 +1,6 @@
-#	$OpenBSD: Makefile.inc,v 1.1 2017/01/11 17:05:29 patrick Exp $
+#	$OpenBSD: Makefile.inc,v 1.2 2017/02/11 06:36:03 jsg Exp $
 
 bootblocks:
 	cp ${DESTDIR}/usr/mdec/BOOTAA64.EFI ${RELEASEDIR}
 
-MDEXT=	bsd.rd BOOTAA64.EFI
+MDEXT=	bsd.rd BOOTAA64.EFI miniroot${OSrev}.fs