cpp_dummy_build: Add missing header psa_util.h

Add missing header to fix #2579.

Change-Id: I038166b826534bac853be34a0281384e26675187
diff --git a/programs/test/cpp_dummy_build.cpp b/programs/test/cpp_dummy_build.cpp
index c652884..9cd5090 100644
--- a/programs/test/cpp_dummy_build.cpp
+++ b/programs/test/cpp_dummy_build.cpp
@@ -81,6 +81,7 @@
 #include "mbedtls/platform_time.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/poly1305.h"
+#include "mbedtls/psa_util.h"
 #include "mbedtls/ripemd160.h"
 #include "mbedtls/rsa.h"
 #include "mbedtls/rsa_internal.h"