CMake: fix build with 3rdparty module enabled through a custom config

Fixes #8165

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/3rdparty/CMakeLists.txt b/3rdparty/CMakeLists.txt
index 14a4674..fa149bd 100644
--- a/3rdparty/CMakeLists.txt
+++ b/3rdparty/CMakeLists.txt
@@ -1,10 +1,2 @@
-execute_process(COMMAND ${MBEDTLS_PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../scripts/config.py -f ${CMAKE_CURRENT_SOURCE_DIR}/../include/mbedtls/mbedtls_config.h get MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED RESULT_VARIABLE everest_result)
-execute_process(COMMAND ${MBEDTLS_PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../scripts/config.py -f ${CMAKE_CURRENT_SOURCE_DIR}/../include/mbedtls/mbedtls_config.h get MBEDTLS_PSA_P256M_DRIVER_ENABLED RESULT_VARIABLE p256m_result)
-
-if(${everest_result} EQUAL 0)
-    add_subdirectory(everest)
-endif()
-
-if(${p256m_result} EQUAL 0)
-    add_subdirectory(p256-m)
-endif()
+add_subdirectory(everest)
+add_subdirectory(p256-m)