Ah, I remembered incorrectly. The targets are adjusted for big acquisitions.
However, for smaller dilution there's two more stockholder protections. The number of shares Musk gets if he achieves the market cap goal is *fixed*.
So as the stock gets diluted, it gets worth less and less as a percentage of shares outstanding, less in terms of control, less in terms of future earning power. So for instance if he doubled the float by issuing stock, his award would be half as much in percentage terms.
On top of that, the award is actually options with a strike price around $350. To the extent that dilution lowers the stock price, it lowers his award's value.
If the market cap is $100 billion and the stock price is below $350 (due to issuing lots of stock), the award is worth nothing. Every stock issuance makes it harder for the award to be worth something.
It's worthless at this point. He hasn't earned any of it.