CI: use Pythran master to build free-threaded wheels [wheel build]

Marking extension modules as thread-safe will only be available
in Pythran 0.17.1, and that is not yet released. This is the last
change needed to ensure the GIL isn't re-enabled on import.

Also add a CI check that no new extension modules without declared
free-threading support sneak back in.

Author: rgommers

tools/wheels/cibw_before_build_linux.sh

@@ -24,8 +24,8 @@ FREE_THREADED_BUILD="$(python -c"import sysconfig; print(bool(sysconfig.get_conf
 if [[ $FREE_THREADED_BUILD == "True" ]]; then
     python -m pip install -U --pre pip
     python -m pip install -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple numpy cython
-    # python -m pip install git+https://github.com/serge-sans-paille/pythran
-    python -m pip install ninja meson-python pybind11 pythran
+    python -m pip install git+https://github.com/serge-sans-paille/pythran
+    python -m pip install ninja meson-python pybind11
 fi
 
 # Install Openblas

tools/wheels/cibw_before_build_macos.sh

@@ -66,8 +66,8 @@ FREE_THREADED_BUILD="$(python -c"import sysconfig; print(bool(sysconfig.get_conf
 if [[ $FREE_THREADED_BUILD == "True" ]]; then
     python -m pip install -U --pre pip
     python -m pip install -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple numpy cython
-    # python -m pip install git+https://github.com/serge-sans-paille/pythran
-    python -m pip install ninja meson-python pybind11 pythran
+    python -m pip install git+https://github.com/serge-sans-paille/pythran
+    python -m pip install ninja meson-python pybind11
 fi
 
 # Install Openblas

tools/wheels/cibw_before_build_win.sh

@@ -17,10 +17,8 @@ FREE_THREADED_BUILD="$(python -c"import sysconfig; print(bool(sysconfig.get_conf
 if [[ $FREE_THREADED_BUILD == "True" ]]; then
     python -m pip install -U --pre pip
     python -m pip install -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple numpy cython
-    # TODO: Remove meson installation from source once a new release
-    # that includes https://github.com/mesonbuild/meson/pull/13851 is available
-    python -m pip install git+https://github.com/mesonbuild/meson
-    python -m pip install ninja meson-python pybind11 pythran
+    python -m pip install git+https://github.com/serge-sans-paille/pythran
+    python -m pip install ninja meson-python pybind11
 fi
 
 # delvewheel is the equivalent of delocate/auditwheel for windows.

tools/wheels/cibw_test_command.sh

@@ -2,10 +2,14 @@ set -xe
 
 FREE_THREADED_BUILD="$(python -c"import sysconfig; print(bool(sysconfig.get_config_var('Py_GIL_DISABLED')))")"
 if [[ $FREE_THREADED_BUILD == "True" ]]; then
-    # TODO: delete when importing numpy no longer enables the GIL
-    # setting to zero ensures the GIL is disabled while running the
-    # tests under free-threaded python
-    export PYTHON_GIL=0
+    # Manually check that importing SciPy does not re-enable the GIL.
+    # In principle the tests should catch this but it seems harmless to leave it
+    # here as a final sanity check before uploading broken wheels
+    if [[ $(python -c "import scipy.stats" 2>&1) == *"The global interpreter lock (GIL) has been enabled"* ]]; then
+        echo "Error: Importing SciPy re-enables the GIL in the free-threaded build"
+        exit 1
+    fi
+
 fi
 
 python -c "import sys; import scipy; sys.exit(not scipy.test())"