You raise a good point. I don't think materials will be a problem once mining is in full swing, but the machines are a factor.

A couple of things may mitigate this.

• The people who make the machines on Earth might be very keen to see them operating on Mars.
• Elon Musk is developing his own chips, which will give him access to machines of his own, particularly in regard to Optimus.
• Elon has the cash to buy what he needs. He will have a plan.
• With Starship's payload capacity, Elon absolutely has the leverage (and likely a detailed plan) to prioritize shipping complete fab lines or critical machines to get things rolling.

It may be a hill to climb, but I don't think it's impassable.