Revert "pythongh-133951: Remove lib64->lib symlink in venv creation (python#137139)"

This reverts commit a7a4855.

Author: StanFromIreland

Lib/test/test_venv.py

@@ -12,6 +12,7 @@
 import pathlib
 import re
 import shutil
+import struct
 import subprocess
 import sys
 import sysconfig
@@ -137,9 +138,14 @@ def _check_output_of_default_create(self):
         self.isdir(self.bindir)
         self.isdir(self.include)
         self.isdir(*self.lib)
+        # Issue 21197
         p = self.get_env_file('lib64')
-        if os.path.exists(p):
-            self.assertFalse(os.path.islink(p))
+        conditions = ((struct.calcsize('P') == 8) and (os.name == 'posix') and
+                      (sys.platform != 'darwin'))
+        if conditions:
+            self.assertTrue(os.path.islink(p))
+        else:
+            self.assertFalse(os.path.exists(p))
         data = self.get_text_file_contents('pyvenv.cfg')
         executable = sys._base_executable
         path = os.path.dirname(executable)

Lib/venv/__init__.py

@@ -174,7 +174,6 @@ def create_if_needed(d):
         context.python_exe = exename
         binpath = self._venv_path(env_dir, 'scripts')
         libpath = self._venv_path(env_dir, 'purelib')
-        platlibpath = self._venv_path(env_dir, 'platlib')
 
         # PEP 405 says venvs should create a local include directory.
         # See https://peps.python.org/pep-0405/#include-files
@@ -192,8 +191,12 @@ def create_if_needed(d):
         create_if_needed(incpath)
         context.lib_path = libpath
         create_if_needed(libpath)
-        context.platlib_path = platlibpath
-        create_if_needed(platlibpath)
+        # Issue 21197: create lib64 as a symlink to lib on 64-bit non-OS X POSIX
+        if ((sys.maxsize > 2**32) and (os.name == 'posix') and
+            (sys.platform != 'darwin')):
+            link_path = os.path.join(env_dir, 'lib64')
+            if not os.path.exists(link_path):   # Issue #21643
+                os.symlink('lib', link_path)
         context.bin_path = binpath
         context.bin_name = os.path.relpath(binpath, env_dir)
         context.env_exe = os.path.join(binpath, exename)