For ${SUBDIR} targets, change the type of dependency operator from `::'

to `:', so that it stays compatible with a stale dependency recorded in
.depend when the type of "foo" changes from file to directory or back.
Compensate for the loss of the "If no sources are specified, the target
is always re-created" feature by marking these targets with the .PHONY
attribute.  While here, fix a bug in the target's script (nobody uses
these targets apparently).

share/mk/bsd.subdir.mk

@@ -57,13 +57,13 @@ _SUBDIR: .USE
 	done
 .endif
 
-${SUBDIR}::
+${SUBDIR}: .PHONY
 	${_+_}@if test -d ${.TARGET}.${MACHINE_ARCH}; then \
 		cd ${.CURDIR}/${.TARGET}.${MACHINE_ARCH}; \
 	else \
 		cd ${.CURDIR}/${.TARGET}; \
 	fi; \
-	${_+_}${MAKE} all
+	${MAKE} all
 
 
 .for __target in all all-man checkdpadd clean cleandepend cleandir \