Source json.h non-locally.

Change-Id: Ia42c41fde74596b394a1f7ae0021f1a5510991a8
diff --git a/tests/ir-tests.cpp b/tests/ir-tests.cpp
index 23c23af..a961e40 100644
--- a/tests/ir-tests.cpp
+++ b/tests/ir-tests.cpp
@@ -7,7 +7,7 @@
 #include "gtest/gtest.h"
 #include "test-utils.hpp"
 extern "C" {
-#include "json.h"
+#include <json.h>
 #include "../cper-parse.h"
 #include "../json-schema.h"
 #include "../generator/cper-generate.h"