Add API tests to cmake build
diff --git a/test/api/test-c.c b/test/api/test-c.c
index 6e8602f..4b43b83 100644
--- a/test/api/test-c.c
+++ b/test/api/test-c.c
@@ -27,7 +27,9 @@
 /* This file tests that all headers can be included from .c files */
 
 
+#ifdef HAVE_CONFIG_H
 #include <config.h>
+#endif
 
 #include <hb.h>