tests: don't build tests unless make check is run

Use check_PROGRAMS instead of noinst_PROGRAMS in tests/Makefile.am
to build the tests only when make check is actually run.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
diff --git a/tests/Makefile.am b/tests/Makefile.am
index b7a7fe7..2ed0e1c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -24,7 +24,7 @@
 TESTS_BGPD =
 endif
 
-noinst_PROGRAMS = testsig testbuffer testmemory heavy heavywq heavythread \
+check_PROGRAMS = testsig testbuffer testmemory heavy heavywq heavythread \
 		testprivs teststream testchecksum tabletest \
 		$(TESTS_BGPD)