add option --disable-tests to disable building of test binaries
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 56e8b6f..0119a02c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1 +1,3 @@
+if ENABLE_TESTS
 SUBDIRS = timer sms
+endif