Make ${CRUNCHBIN}.mk depend on ${TOOL_CRUNCHGEN:[-1]} instead of .PHONY.

Recreating the makefile when the crunchgen program has changed is probably
adequate, and it allows a lot of later optimisations to still apply.
In particular:
- the final link for ramdiskbin
- the create of the embedded filesystem
- the inclusion of the ramdisk into the kernel
- compressing the kernel
Unless something else actually requires one of the above.

distrib/common/Makefile.crunch

@@ -1,4 +1,4 @@
-#	$NetBSD: Makefile.crunch,v 1.19 2005/02/10 16:03:34 jmc Exp $
+#	$NetBSD: Makefile.crunch,v 1.20 2005/09/04 19:00:40 dsl Exp $
 #
 # Makefile snippet to build a crunchgen(1)ed binary from the provided lists
 #
@@ -48,7 +48,7 @@ ${CRUNCHBIN}.c: ${CRUNCHBIN}.mk
 ${CRUNCHBIN}.cache: ${CRUNCHBIN}.mk
 	[ ! -f ${.TARGET} ] || touch ${.TARGET}
 
-${CRUNCHBIN}.mk: ${CRUNCHBIN}.conf .PHONY
+${CRUNCHBIN}.mk: ${CRUNCHBIN}.conf  ${TOOL_CRUNCHGEN:[-1]}
 	${CRUNCHENV} ${TOOL_CRUNCHGEN} -f -D ${NETBSDSRCDIR} \
 	    -L ${DESTDIR}/usr/lib -q ${CRUNCHGEN_FLAGS} ${.ALLSRC}