Change include style to use system includes

The libcper header files in `libcper` are installed to
`usr/include/libcper`. Use that system includes in `libcper` source
instead of using the project includes.

Change-Id: I596edc2c754dae4829844f535a1e34caa246fb43
Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>
diff --git a/tests/test-utils.hpp b/tests/test-utils.hpp
index af9390e..38e24a7 100644
--- a/tests/test-utils.hpp
+++ b/tests/test-utils.hpp
@@ -2,7 +2,7 @@
 #define CPER_IR_TEST_UTILS_H
 
 extern "C" {
-#include "BaseTypes.h"
+#include <libcper/BaseTypes.h>
 }
 
 FILE *generate_record_memstream(const char **types, UINT16 num_types,