lttng-tools: make the dependency on lttng-libust optional

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/lttng-tools/Config.in

@@ -3,7 +3,6 @@ config BR2_PACKAGE_LTTNG_TOOLS
 	depends on BR2_PACKAGE_LTTNG_MODULES
 	select BR2_PACKAGE_LIBURCU
 	select BR2_PACKAGE_POPT
-	select BR2_PACKAGE_LTTNG_LIBUST
 	help
 	  Userspace utilities for the LTTng 2.0 tracing
 	  infrastructure.
@@ -17,4 +16,7 @@ config BR2_PACKAGE_LTTNG_TOOLS
 	  package for the target, if babeltrace on the target is
 	  interesting.
 
+	  If userspace tracing is desired, you need to enable
+	  lttng-libust.
+
 	  http://lttng.org

package/lttng-tools/lttng-tools.mk

@@ -6,8 +6,15 @@ LTTNG_TOOLS_SOURCE  = lttng-tools-$(LTTNG_TOOLS_VERSION).tar.bz2
 # dependency. However, having the babeltrace utilities built for the
 # host is very useful, since those tools allow to convert the binary
 # trace format into an human readable format.
-LTTNG_TOOLS_DEPENDENCIES = liburcu popt host-lttng-babeltrace lttng-libust
+LTTNG_TOOLS_DEPENDENCIES = liburcu popt host-lttng-babeltrace
 
 LTTNG_AUTORECONF = YES
 
+ifeq ($(BR2_PACKAGE_LTTNG_LIBUST),y)
+LTTNG_TOOLS_CONF_OPT += --enable-lttng-ust
+LTTNG_TOOLS_DEPENDENCIES += lttng-libust
+else
+LTTNG_TOOLS_CONF_OPT += --disable-lttng-ust
+endif
+
 $(eval $(call AUTOTARGETS))