TST: ensure test_extending compile tests work with any meson

The `meson` executable isn't guaranteed to be installed for the same
Python interpreter as we're running the tests for (this may for example
happen in distro setups when we're testing a non-default Python).
Explicitly passing the Python interpreter we're testing for to Meson
via a native file should be a robust solution.

scipy/_lib/_testutils.py

@@ -280,20 +280,35 @@ def _test_cython_extension(tmp_path, srcdir):
     Helper function to test building and importing Cython modules that
     make use of the Cython APIs for BLAS, LAPACK, optimize, and special.
     """
+    try:
+        subprocess.check_call(["meson", "--version"])
+    except FileNotFoundError:
+        pytest.skip("No usable 'meson' found")
+
     # build the examples in a temporary directory
     mod_name = os.path.split(srcdir)[1]
     shutil.copytree(srcdir, tmp_path / mod_name)
     build_dir = tmp_path / mod_name / 'tests' / '_cython_examples'
     target_dir = build_dir / 'build'
     os.makedirs(target_dir, exist_ok=True)
+
+    # Ensure we use the correct Python interpreter even when `meson` is
+    # installed in a different Python environment (see numpy#24956)
+    native_file = str(build_dir / 'interpreter-native-file.ini')
+    with open(native_file, 'w') as f:
+        f.write("[binaries]\n")
+        f.write(f"python = '{sys.executable}'")
+
     if sys.platform == "win32":
         subprocess.check_call(["meson", "setup",
                                "--buildtype=release",
+                               "--native-file", native_file,
                                "--vsenv", str(build_dir)],
                               cwd=target_dir,
                               )
     else:
-        subprocess.check_call(["meson", "setup", str(build_dir)],
+        subprocess.check_call(["meson", "setup",
+                               "--native-file", native_file, str(build_dir)],
                               cwd=target_dir
                               )
     subprocess.check_call(["meson", "compile", "-vv"], cwd=target_dir)