Ecclesiastes 2:26

Now we are beginning to see another factor. Is it better to receive a gift from God or is it better to work for that gift (if I can put it that way) in the way Solomon did? It is better that it be given by God. What he is saying is that God can turn—with your understanding, with your help—something that would normally be meaningless and absurd into something that is profitable for you, if you will let Him. To the person "who is good in His sight."

This is an overall conclusion he has reached here—that eventually the evil on the earth are working for the benefit of the righteous. Eventually all is going to come to those God considers good.

Solomon is looking at this in a very long range way. Eventually, if a person is righteous, the wicked have been out there building and gathering for the work of the righteous. All that they are doing is a vanity to them, but it is a gift to the righteous from God.