bpo-1294959: Add sys.platlibdir attribute (GH-18381)

Add --with-platlibdir option to the configure script: name of the
platform-specific library directory, stored in the new sys.platlitdir
attribute. It is used to build the path of platform-specific dynamic
libraries and the path of the standard library.

It is equal to "lib" on most platforms. On Fedora and SuSE, it is
equal to "lib64" on 64-bit systems.

Co-Authored-By: Jan Matějek <jmatejek@suse.com>
Co-Authored-By: Matěj Cepl <mcepl@cepl.eu>
Co-Authored-By: Charalampos Stratakis <cstratak@redhat.com>
diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index 46ed113..444097b 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -1068,11 +1068,11 @@
         else:
             ver = sys.version_info
             return [
-                os.path.join(prefix, 'lib',
+                os.path.join(prefix, sys.platlibdir,
                              f'python{ver.major}{ver.minor}.zip'),
-                os.path.join(prefix, 'lib',
+                os.path.join(prefix, sys.platlibdir,
                              f'python{ver.major}.{ver.minor}'),
-                os.path.join(exec_prefix, 'lib',
+                os.path.join(exec_prefix, sys.platlibdir,
                              f'python{ver.major}.{ver.minor}', 'lib-dynload'),
             ]
 
@@ -1183,7 +1183,7 @@
 
             if not MS_WINDOWS:
                 lib_dynload = os.path.join(pyvenv_home,
-                                           'lib',
+                                           sys.platlibdir,
                                            f'python{ver.major}.{ver.minor}',
                                            'lib-dynload')
                 os.makedirs(lib_dynload)