Pro-life advocates give the example of a brick-layer building a house.
Even if he has laid down only a few bricks, it would be wrong to
demolish whatever he has constructed.

Actually, this analogy is inaccurate. The brick-layer is a full-fledged
person, who is fully conscious, fully sentient, and is endowed with
inarguable human rights. Tearing down his wall is an obvious crime.

But let's alter this example to make it more accurate for abortion.
Suppose the brick-layer, at least initially, were a robot. For the first
two-thirds of the project, it would do all the work, and then hang out a
sign that said, "This house is free to any humans willing to finish the
job."

When the humans arrived (inevitably so, for the house is free), the
robot would gradually phase itself out, showing the humans where the
materials were, what paint was available, etc. But eventually it would
phase itself out completely.

Now suppose that, during the first two-thirds of construction, the mayor
of the city came along and discovered that the robot was building a
house in the middle of the road. The mayor, of course, has only the
highest praise for free housing. Nonetheless, he stops the robot and
directs it to a better location.

Has the mayor violated the rights of the robot? Of course not.

Has the mayor violated the rights of the future tenants? Of course not.
They do not even know who they were.

And it would certainly be strange if a protest group argued to the mayor
that free housing is such a sacred right that houses should be allowed
to go up wherever they start, even in the middle of roads. If anything,
it is the mayor who is more caring and concerned, and not this bizarre
protest group.