Automatically append SUBDIR.yes to the SUBDIR variable, and

remove duplicates. We cannot sort SUBDIR because many Makefiles
have .WAIT in the list which is strongly ordering. Rather than
try to second guess when to sort and when to not sort depending
on .WAIT being in the list, just remove duplicates.

share/mk/bsd.subdir.mk

@@ -16,7 +16,8 @@
 #
 # SUBDIR	A list of subdirectories that should be built as well.
 #		Each of the targets will execute the same target in the
-#		subdirectories.
+#		subdirectories. SUBDIR.yes is automatically appeneded
+#		to this list.
 #
 # +++ targets +++
 #
@@ -43,6 +44,11 @@ _SUBDIR:
 .endif
 .if !target(_SUBDIR)
 
+.if defined(SUBDIR)
+SUBDIR:=${SUBDIR} ${SUBDIR.yes}
+SUBDIR:=${SUBDIR:u}
+.endif
+
 DISTRIBUTION?=	base
 .if !target(distribute)
 distribute: .MAKE