Adapt sources to configurable config.h name
diff --git a/tests/scripts/generate_code.pl b/tests/scripts/generate_code.pl
index 6c2ac6e..6cba14f 100755
--- a/tests/scripts/generate_code.pl
+++ b/tests/scripts/generate_code.pl
@@ -59,7 +59,11 @@
 
 open(TEST_FILE, ">$test_file") or die "Opening destination file '$test_file': $!";
 print TEST_FILE << "END";
+#if !defined(POLARSSL_CONFIG_FILE)
 #include <polarssl/config.h>
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
 
 $suite_pre_code
 $suite_header