Add a makefle that recurses into the right architecture-specific

sub-directory. This to allow simpler logic outside of the csu
directory.

Obtained from:	Juniper Networks, Inc.

lib/csu/Makefile

@@ -0,0 +1,10 @@
+# $FreeBSD$
+
+ARCH= ${MACHINE_ARCH:S/i386/i386-elf/}
+.if exists(${.CURDIR}/${ARCH})
+SUBDIR+= ${ARCH}
+.else
+SUBDIR+= ${MACHINE_CPUARCH}
+.endif
+
+.include <bsd.subdir.mk>