Fix the build when MBEDTLS_PLATFORM_C is unset

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/programs/test/dlopen.c b/programs/test/dlopen.c
index 3b88df4..c083604 100644
--- a/programs/test/dlopen.c
+++ b/programs/test/dlopen.c
@@ -19,8 +19,9 @@
 
 #include "mbedtls/build_info.h"
 
+#if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
-#if !defined(MBEDTLS_PLATFORM_C)
+#else
 #include <stdio.h>
 #include <stdlib.h>
 #define mbedtls_fprintf    fprintf