Is it possible to use vanity keypairs in anchor Programs

The keypairs generated for anchor programs are random, for instance
using “anchor keys list” I see that my generated key is:

declare_id!(“Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS”);

Can we use our own generated vanity keys? or they must be always automatically generated by using: anchor build ??