If it's a custom distro made by the miner's manufacturer then why doesn't the miner work on it and have you asked them about it? I'm sorry to keep coming back to this but using a distro made by some random person with no support and no comebacks surely just means you're making money for somebody else?
I have not done what you are trying to do but I would suggest that you take a step back and think about what you can and cannot achieve here as is seems you've jumped into something you don't understand without looking beforehand.

I don't really get your point. Its my miner, I purchased it, I own it. What do you mean by 'making money for somebody else'?
All I want is to improve its functionality. For myself only.

I mean that so far all you have told us is that you have an unknown distribution on which you can't install something. If you bought some kind of "bitcoin miner" package then have you tried to ask the support of the people you bought it from? This is evidently not a standard Raspian install.
The reason I say making money for somebody else is that if you really do not know what operating system and programs are installed on the device you have no way of knowing what it is doing when so for all you know it is only mining currency for the person who put together the operating system, whatever that is.

Asking the customer support is one of the first thing I've tried, but they are unresponsive.
I just need help on installing gcc. Thanks.