It is a problem with your lot, not the house.
And 'hairline' cracks even in a properly designed and installed slab is considered quite normal.
Unless you can prove by a soil engineer's anaylysis of the ground and by a structural engineer's analysis of the house that the builder was negligent in constructing the house on expansive clay soil, there is little you can do but use a different type of flooring.
I can't see the cracks from here.
But many hairline cracks are indeed normal and may be more from shrinkage than from foundation movement.
To assess your individdual problem, you need an experienced contractor or - better - an independent experienced home inspector. This would be your nickle as it would be your burden of proof if you believe you have been wronged by the builder.
You probably have nothing to be concerned about and shrinkage cracks only that can be regrouted. However, if the tiles themselves are cracked, this may indicate foundation movement. I will disagree with the previous poster on this. A builder should not place a foundation directly on expansive soils. By trenching and replacing with good gravel and drainage, he can re-engineer the site before building to avoid problems. Your builder may have scrimped on this step.
The cracks are indeed on the tiles. The grouts in between are good, except at the bottom of the shower stall where grouts usualy crack. I forgot to mention these tiles are around the tub and on the shower wall.
I thought however they prepared the soil for other lots, they also did for mine. My lot elevation is a little higher on this street. None of my neighbors have this problem. All houses in this development are on post tension slabs.