Here are the sentences including the word.
まあ こんなところでよかろう まったくよくもくだらん まねばかりしおって
I'm not sure if it is a colloquial form of 「しまう」.
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It's not related to しまう. おる in this context is an auxiliary verb which is described in this definition:
Basically it's a word to show one's disgust. I think there's no direct equivalent auxiliary verb in English, but you can use anything that can make a sentence dirty and rough; "hell", "shit", etc.
The Osaka-ben equivalent is よる (eg まねばかりしよって), which may be more commonly heard in the daily life of an ordinary person.