autoconfigArtifacts overide default from other runtime environments.

[hansheng654]

when using multiple languages in one serverless, not all language requires artifact field to be set. You will get below error:

This is due to line 44 below automatically forcing all other languages to use the same buildDir as Python. I have to add line 43 to bypass such operation. so that other plugins can work properly and set their own artifact directory

Please help make this official, by simply do a check on the runtime is python or not.