Fix building with a dev manager

Makefile

@@ -7,6 +7,7 @@ SRCS+=		dhcp-common.c
 
 CFLAGS?=	-O2
 CSTD?=		c99
+MKDIRS=
 include config.mk
 CFLAGS+=	-std=${CSTD}
 
@@ -27,7 +28,7 @@ CLEANFILES+=	.depend
 FILES=		dhcpcd.conf
 FILESDIR=	${SYSCONFDIR}
 
-SUBDIRS=	dhcpcd-hooks dev
+SUBDIRS=	dhcpcd-hooks ${MKDIRS}
 
 SED_DBDIR=		-e 's:@DBDIR@:${DBDIR}:g'
 SED_LIBDIR=		-e 's:@LIBDIR@:${LIBDIR}:g'

configure

@@ -607,10 +607,9 @@ if [ "$DEV" != no -a "$UDEV" != no ]; then
 	printf "Checking for libudev ... "
 	LIBUDEV_CFLAGS=$(pkg-config --cflags libudev 2>/dev/null)
 	LIBUDEV_LIBS=$(pkg-config --libs libudev 2>/dev/null)
-	[ -z "$DEV" ] && DEV=yes
 fi
 if [ "$DEV" != no -a "$UDEV" != no -a -n "$LIBUDEV_LIBS" ]; then
-	echo "yes"
+	[ -z "$DEV" ] && DEV=yes
 	echo "DEV_PLUGINS+=	udev" >>$CONFIG_MK
 	if [ -n "$LIBUDEV_CFLAGS" ]; then
 		echo "LIBUDEV_CFLAGS=		$LIBUDEV_CFLAGS" >>$CONFIG_MK
@@ -641,7 +640,8 @@ fi
 if [ "$DEV" = yes ]; then
 	echo "SRCS+=		dev.c" >>$CONFIG_MK
 	echo "CPPFLAGS+=	-DPLUGIN_DEV" >>$CONFIG_MK
-	echo "LDFLAGS+=		-Wl,--export-dynamic" >>$CONFIG_MK
+	echo "LDFLAGS+=	-Wl,--export-dynamic" >>$CONFIG_MK
+	echo "MKDIRS+=		dev"
 fi
 
 if [ -z "$SERVICECMD" ]; then

dev.h

@@ -46,8 +46,8 @@ void dev_stop(void);
 #else
 #define dev_initialized(a) 1
 #define dev_listening() 0
-#define dev_start(a)
-#define dev_stop()
+#define dev_start(a) {}
+#define dev_stop() {}
 #endif
 
 #endif