Don't install cython on pypy (breaks coverage with it's plugin). Also build exts on freethreading.

Author: ionelmc

tox.ini

@@ -14,7 +14,7 @@ envlist =
     clean,
     check,
     docs,
-    {py39,py310,py311,py312,py313,py313-ft,pypy39,pypy310}-{pure,cython}-{cover,nocov},
+    {py39,py310,py311,py312,py313,py313-ft,pypy39,pypy310,pypy310}-{pure,cython}-{cover,nocov},
     report
 ignore_basepython_conflict = true
 
@@ -45,7 +45,7 @@ deps =
     pytest
     pytest-benchmark
     cover: pytest-cov
-    cython
+    {py38,py39,py310,py311,py312,py313,py313ft}: cython
     manhole
     process-tests
     setuptools-scm
@@ -55,8 +55,8 @@ deps =
     tzdata
     ipdb
 commands =
-    {py38,py39,py310,py311,py312,py313}: python tests/setup.py clean --all
-    {py38,py39,py310,py311,py312,py313}: python tests/setup.py build_ext --force --inplace
+    {py38,py39,py310,py311,py312,py313,py313ft}: python tests/setup.py clean --all
+    {py38,py39,py310,py311,py312,py313,py313ft}: python tests/setup.py build_ext --force --inplace
     cover: python setup.py clean --all build_ext --force --inplace
     nocov: {posargs:pytest -vv --ignore=src}
     cover: {posargs:pytest --cov --cov-report=term-missing -vv}