configure: Enable valgrind support

I've caught some issues with valgrind that were missed by the compiler
sanitizers (though were interestingly picked up by the cmake build of
the test suites).

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I96ac0a331c2d7466ee66a7ce2e8d8b2b8d497d5d
diff --git a/Makefile.am b/Makefile.am
index 75535d4..d630078 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -49,3 +49,5 @@
 noinst_LIBRARIES = tests/libtest-utils.a
 
 tests_libtest_utils_a_SOURCES = tests/test-utils.c tests/test-utils.h
+
+@VALGRIND_CHECK_RULES@