fix: match new extension discovery with changes to classic discovery (#2640)

* fix: match new extension discovery with changes to classic discovery

Followup to #2638 - this was fixed in 2.6.0, but only for classic Python

* fix: followup to avoid warnings

tools/FindPythonLibsNew.cmake

@@ -115,7 +115,7 @@ print('.'.join(str(v) for v in sys.version_info));
 print(sys.prefix);
 print(sys.prefix);
 print(s.get_python_inc(plat_specific=True));
 print(s.get_python_inc(plat_specific=True));
 print(s.get_python_lib(plat_specific=True));
 print(s.get_python_lib(plat_specific=True));
-print(s.get_config_var('SO') or s.get_config_var('EXT_SUFFIX'));
+print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'));
 print(hasattr(sys, 'gettotalrefcount')+0);
 print(hasattr(sys, 'gettotalrefcount')+0);
 print(struct.calcsize('@P'));
 print(struct.calcsize('@P'));
 print(s.get_config_var('LDVERSION') or s.get_config_var('VERSION'));
 print(s.get_config_var('LDVERSION') or s.get_config_var('VERSION'));

tools/pybind11NewTools.cmake

@@ -95,8 +95,9 @@ endif()
 # required for PyPy3 (as of 7.3.1)
 # required for PyPy3 (as of 7.3.1)
 if(NOT DEFINED PYTHON_MODULE_EXTENSION)
 if(NOT DEFINED PYTHON_MODULE_EXTENSION)
   execute_process(
   execute_process(
-    COMMAND "${${_Python}_EXECUTABLE}" "-c"
-            "from distutils import sysconfig; print(sysconfig.get_config_var('SO'))"
+    COMMAND
+      "${${_Python}_EXECUTABLE}" "-c"
+      "from distutils import sysconfig as s;print(s.get_config_var('EXT_SUFFIX') or s.get_config_var('SO'))"
     OUTPUT_VARIABLE _PYTHON_MODULE_EXTENSION
     OUTPUT_VARIABLE _PYTHON_MODULE_EXTENSION
     ERROR_VARIABLE _PYTHON_MODULE_EXTENSION_ERR
     ERROR_VARIABLE _PYTHON_MODULE_EXTENSION_ERR
     OUTPUT_STRIP_TRAILING_WHITESPACE)
     OUTPUT_STRIP_TRAILING_WHITESPACE)