fix test_cmake_as_package fail

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 0fb46d6..add0784 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -151,6 +151,8 @@
         COMMAND
             ${MBEDTLS_PYTHON_EXECUTABLE}
                 ${CMAKE_CURRENT_SOURCE_DIR}/../scripts/generate_ssl_debug_helpers.py
+                --mbedtls-root ${CMAKE_CURRENT_SOURCE_DIR}/..
+                ${CMAKE_CURRENT_BINARY_DIR}
         DEPENDS
             ${CMAKE_CURRENT_SOURCE_DIR}/../scripts/generate_ssl_debug_helpers.py
             ${error_headers}