CI: Pass IDF_PATH to build_system_tests.sh

.gitlab-ci.yml

@@ -28,6 +28,8 @@ test_nvs_on_host:
 test_build_system:
   stage: test
   image: espressif/esp32-ci-env
+  variables:
+    IDF_PATH: "$CI_PROJECT_DIR"
   script:
     - ./make/build_system_tests.sh