Test the PSA alternative header configuration macros

Test that MBEDTLS_PSA_CRYPTO_PLATFORM_FILE and
MBEDTLS_PSA_CRYPTO_STRUCT_FILE can be set to files in a directory that comes
after the standard directory in the include file search path.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/programs/test/query_included_headers.c b/programs/test/query_included_headers.c
new file mode 100644
index 0000000..383a2ff
--- /dev/null
+++ b/programs/test/query_included_headers.c
@@ -0,0 +1,41 @@
+/* Ad hoc report on included headers. */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#include <psa/crypto.h>
+#include <mbedtls/platform.h>
+
+int main(void)
+{
+
+    /* Which PSA platform header? */
+#if defined(PSA_CRYPTO_PLATFORM_H)
+    mbedtls_printf("PSA_CRYPTO_PLATFORM_H\n");
+#endif
+#if defined(PSA_CRYPTO_PLATFORM_ALT_H)
+    mbedtls_printf("PSA_CRYPTO_PLATFORM_ALT_H\n");
+#endif
+
+    /* Which PSA struct header? */
+#if defined(PSA_CRYPTO_STRUCT_H)
+    mbedtls_printf("PSA_CRYPTO_STRUCT_H\n");
+#endif
+#if defined(PSA_CRYPTO_STRUCT_ALT_H)
+    mbedtls_printf("PSA_CRYPTO_STRUCT_ALT_H\n");
+#endif
+
+}