trivial: allow building tests from rdisc directory

The nm-rdisc subsystem, just as the nm-platform subsystem is separately
testable and it proved convenient to be able to build the test programs
by just typing 'make' in the rdisc/platform directory where the source
code for those modules resides.

configure.ac

@@ -689,6 +689,7 @@ src/settings/plugins/example/Makefile
 src/settings/tests/Makefile
 src/platform/Makefile
 src/platform/tests/Makefile
+src/rdisc/Makefile
 src/rdisc/tests/Makefile
 src/devices/wimax/Makefile
 libnm-util/libnm-util.pc

src/Makefile.am

@@ -13,13 +13,13 @@ SUBDIRS += devices/wimax
 endif
 
 if ENABLE_TESTS
-SUBDIRS +=				\
-	config/tests			\
-	dhcp-manager/tests		\
-	platform			\
-	settings/tests			\
-	supplicant-manager/tests	\
-	rdisc/tests			\
+SUBDIRS += \
+	config/tests \
+	dhcp-manager/tests \
+	platform \
+	rdisc \
+	settings/tests \
+	supplicant-manager/tests \
 	tests
 endif
 

src/rdisc/Makefile.am

@@ -0,0 +1 @@
+SUBDIRS = tests