Build: Enable linking with PSA API compliance tests in the NS app

This change modifies the build system to support linking
the PSA API compliance test static libraries. It introduces
a new build configuration ConfigPsaApiTest.cmake for this purpose.
The build instructions are updated to show an example of how
to use this new build configuration.

Change-Id: Iabf4876504e690826fe80b467a91fa53bffb0b47
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
Co-Authored-by: Antonio de Angelis <antonio.deangelis@arm.com>
diff --git a/interface/src/tfm_nspm_api.c b/interface/src/tfm_nspm_api.c
index dc5e645..a835f2d 100644
--- a/interface/src/tfm_nspm_api.c
+++ b/interface/src/tfm_nspm_api.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2019, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -28,6 +28,9 @@
     {"seq_task", -5},
     {"mid_task", -6},
     {"pri_task", -7},
+#ifdef PSA_API_TEST_NS
+    {"psa_api_test", -8}
+#endif
 };
 
 /**