linux-builder config...diskSize changes does not get applied unless ephemeral

[gustafj]

When changing the max size for the VM backing storage of the linux-builder the change has no effect unless the nixos.qcow2 is manually removed or nix.linux-builder.ephemeral = true.
I do not know if this is only for the disk or for other parameters on the builder as well.
Would be nice if this is at least mentioned in the documentation at least or better yet a warning is given.

nix.linux-builder = {
  enable = true;
  config = {
    virtualisation = {
      darwin-builder = {
        diskSize = 80 * 1024;
      };
    };
  };
};