package/rauc: d-bus support is optional

As pointed out by Jan Lübbe, D-Bus support is optional:

> You can build without D-Bus (./configure --disable-service).

So drop it from the required dependencies and add a RAUC_DBUS sub option
like it is done for network/json.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rauc/Config.in

@@ -5,7 +5,6 @@ config BR2_PACKAGE_RAUC
 	depends on BR2_USE_WCHAR # glib2
 	select BR2_PACKAGE_LIBGLIB2
 	select BR2_PACKAGE_OPENSSL
-	select BR2_PACKAGE_DBUS
 	select BR2_PACKAGE_SQUASHFS # run-time dependency
 	select BR2_PACKAGE_UBOOT_TOOLS if BR2_TARGET_UBOOT # run-time dependency
 	select BR2_PACKAGE_UBOOT_TOOLS_FWPRINTENV if BR2_TARGET_UBOOT
@@ -19,6 +18,13 @@ config BR2_PACKAGE_RAUC
 
 if BR2_PACKAGE_RAUC
 
+config BR2_PACKAGE_RAUC_DBUS
+	bool "dbus support"
+	select BR2_PACKAGE_DBUS
+	help
+	  This option enables support for controlling rauc through
+	  D-Bus.
+
 config BR2_PACKAGE_RAUC_NETWORK
 	bool "network support"
 	select BR2_PACKAGE_LIBCURL

package/rauc/rauc.mk

@@ -10,7 +10,14 @@ RAUC_SOURCE = rauc-$(RAUC_VERSION).tar.xz
 RAUC_LICENSE = LGPL-2.1
 RAUC_LICENSE_FILES = COPYING
 RAUC_CPE_ID_VENDOR = pengutronix
-RAUC_DEPENDENCIES = host-pkgconf openssl libglib2 dbus
+RAUC_DEPENDENCIES = host-pkgconf openssl libglib2
+
+ifeq ($(BR2_PACKAGE_RAUC_DBUS),y)
+RAUC_CONF_OPTS += --enable-service
+RAUC_DEPENDENCIES += dbus
+else
+RAUC_CONF_OPTS += --disable-service
+endif
 
 ifeq ($(BR2_PACKAGE_RAUC_NETWORK),y)
 RAUC_CONF_OPTS += --enable-network