cmake: Generate test_keys.h and test_certs.h in the build tree

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ef57df9..c981ef7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -355,35 +355,37 @@
     if(GEN_FILES)
         add_custom_command(
             OUTPUT
-                ${CMAKE_CURRENT_SOURCE_DIR}/framework/tests/include/test/test_keys.h
-            WORKING_DIRECTORY
-                ${CMAKE_CURRENT_SOURCE_DIR}/tests
+                ${CMAKE_CURRENT_BINARY_DIR}/tests/include/test/test_keys.h
+            COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_BINARY_DIR}/tests/include/test
             COMMAND
                 "${MBEDTLS_PYTHON_EXECUTABLE}"
                 "${CMAKE_CURRENT_SOURCE_DIR}/framework/scripts/generate_test_keys.py"
                 "--output"
-                "${CMAKE_CURRENT_SOURCE_DIR}/framework/tests/include/test/test_keys.h"
+                "${CMAKE_CURRENT_BINARY_DIR}/tests/include/test/test_keys.h"
             DEPENDS
                 ${CMAKE_CURRENT_SOURCE_DIR}/framework/scripts/generate_test_keys.py
         )
-        add_custom_target(test_keys_header DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/framework/tests/include/test/test_keys.h)
+        add_custom_target(test_keys_header
+            DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/tests/include/test/test_keys.h)
         add_custom_command(
             OUTPUT
-                ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/test_certs.h
+                ${CMAKE_CURRENT_BINARY_DIR}/tests/include/test/test_certs.h
+            COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_BINARY_DIR}/tests/include/test
             WORKING_DIRECTORY
                 ${CMAKE_CURRENT_SOURCE_DIR}/tests
             COMMAND
                 "${MBEDTLS_PYTHON_EXECUTABLE}"
                 "${CMAKE_CURRENT_SOURCE_DIR}/framework/scripts/generate_test_cert_macros.py"
                 "--output"
-                "${CMAKE_CURRENT_SOURCE_DIR}/tests/src/test_certs.h"
+                "${CMAKE_CURRENT_BINARY_DIR}/tests/include/test/test_certs.h"
             DEPENDS
                 ${CMAKE_CURRENT_SOURCE_DIR}/framework/scripts/generate_test_cert_macros.py
         )
-        add_custom_target(test_certs_header DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/test_certs.h)
+        add_custom_target(test_certs_header DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/tests/include/test/test_certs.h)
         add_dependencies(mbedtls_test test_keys_header test_certs_header)
     endif()
     target_include_directories(mbedtls_test
+        PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/tests/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/framework/tests/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/tests/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include