Enable valgrind in tests/ when enabled by configure

Signed-off-by: Tim Rühsen <tim.ruehsen@gmx.de>
diff --git a/tests/Makefile.am b/tests/Makefile.am
index b0fe211..2e54764 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -101,3 +101,5 @@
 	EXEEXT=$(EXEEXT) \
 	LSAN_OPTIONS=suppressions=libtasn1.supp \
 	$(VALGRIND)
+
+LOG_COMPILER ?= $(VALGRIND)