Use "build" for building

Instead of directly running setup.py.

This allows Python 3.12 (as well as previous versions) to be used
for building. Although setuptools could be added as a development
dependency to run setup.py, using "build" instead is recommended in
https://setuptools.pypa.io/en/latest/userguide/quickstart.html.

Those docs likewise recommend only listing "wheel" in the
build-system section of pyproject.toml if setup.py actually imports
the wheel module. So this removes that. (Running "make release",
which now uses "build", will continue to build wheels.)

The "build" package is not conceptually a testing dependency, but
test-requirements.txt is currently the de facto list of all stable
development dependencies for regular use.

Makefile

@@ -16,5 +16,5 @@ release: clean
 
 force_release: clean
 	git push --tags origin main
-	python3 setup.py sdist bdist_wheel
+	python -m build --sdist --wheel
 	twine upload dist/*

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools", "wheel"]
+requires = ["setuptools"]
 build-backend = "setuptools.build_meta"
 
 [tool.pytest.ini_options]

test-requirements.txt

@@ -5,6 +5,7 @@ black
 
 pre-commit
 
+build
 virtualenv
 
 pytest