Fix symbol definition conflict in tools (#5554)

tools/test/h5diff/h5diffgentest.c

@@ -14,18 +14,8 @@
 #include "H5private.h"
 #include "h5gentest.h"
 #include "h5diffgentest.h"
-
-/*
- * The output functions need a temporary buffer to hold a piece of the
- * dataset while it's being printed. This constant sets the limit on the
- * size of that temporary buffer in bytes. For efficiency's sake, choose the
- * largest value suitable for your machine (for testing use a small value).
- */
-/* Maximum size used in a call to malloc for a dataset
- * NOTE: this value should stay in sync with the value defined in the tools
- *       library file: h5tools_utils.h
- */
-size_t H5TOOLS_MALLOCSIZE = (128 * 1024 * 1024);
+#include "h5tools.h"
+#include "h5tools_utils.h"
 
 #define UIMAX    4294967295u /*Maximum value for a variable of type unsigned int */
 #define STR_SIZE 3