[fix] utils/build_env.py: make sure to always use searx/settings.yml

ignore SEARX_SETTINGS_PATH

[1] https://github.com/searx/searx/pull/2408#pullrequestreview-565247895



Suggested-by: @dalf [1]
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>