Remove deprecated use of distutils, fix for Python 3.12+

This switches to using sysconfig from distutils, which is necessary for
Python 3.12+ since distutils is deprecated and has been removed.

It is necessary to specify the install scheme when a prefix other than
the Python default is used so that changes to the default scheme made by
distributions (e.g. Debian, Fedora) do not produce an incorrect Python
installation directory. For example, Debian patches the default scheme
to prepend the path with '/local', but if a user specifies a prefix of
'/usr/local', then the path using the default scheme would be
'/usr/local/local/...' with a duplicated 'local' directory. Specifying
an unmodified install scheme fixes that.

Signed-off-by: Ryan Volz <ryan.volz@gmail.com>

swig/python/get_python_lib.py

@@ -1,19 +1,33 @@
 import os
+import pathlib
 import sys
-import site
-from distutils.sysconfig import get_python_lib
+import sysconfig
 
 if __name__ == '__main__':
-    prefix = sys.argv[1]
+    prefix = pathlib.Path(sys.argv[1]).resolve()
 
-    #ask distutils where to install the python module
-    install_dir = get_python_lib(plat_specific=True, prefix=prefix)
+    # default install dir for the running Python interpreter
+    default_install_dir = pathlib.Path(sysconfig.get_path('platlib')).resolve()
 
-    #use sites when the prefix is already recognized
+    # if default falls under the desired prefix, we're done
     try:
-        paths = [p for p in site.getsitepackages() if p.startswith(prefix)]
-        if len(paths) == 1: install_dir = paths[0]
-    except AttributeError: pass
+        relative_install_dir = default_install_dir.relative_to(prefix)
+    except ValueError:
+        # get install dir for the specified prefix
+        # can't use the default scheme because distributions modify it
+        # newer Python versions have 'venv' scheme, use for all OSs.
+        if 'venv' in sysconfig.get_scheme_names():
+            scheme = 'venv'
+        elif os.name == 'nt':
+            scheme = 'nt'
+        else:
+            scheme = 'posix_prefix'
+        prefix_install_dir = pathlib.Path(sysconfig.get_path(
+            'platlib',
+            scheme=scheme,
+            vars={'base': prefix, 'platbase': prefix},
+        )).resolve()
+        relative_install_dir = prefix_install_dir.relative_to(prefix)
 
-    #strip the prefix to return a relative path
-    print(os.path.relpath(install_dir, prefix))
+    # want a relative path for use in the build system
+    print(relative_install_dir)