Direct use of "setup.py sdist" is deprecated. Instead we use build to create the sdists.

We add new targets make sagemath_objects-sdist etc.

We move targets make pypi-sdists (which now uses the new targets), make wheel, and make pypi-wheels from the top-level Makefile to build/make/Makefile.in. This improves make pypi-wheels: It no longer builds the sagemath-objects wheel multiple times (as dependencies of other packages).

Depends on #34858

CC: @kiwifb

Component: build

Author: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/34855