bpo-31904: Fix site and sysconfig modules for VxWorks RTOS (GH-21821)

diff --git a/Lib/test/test_site.py b/Lib/test/test_site.py
index 2e70880..6060288 100644
--- a/Lib/test/test_site.py
+++ b/Lib/test/test_site.py
@@ -36,6 +36,7 @@
 import site
 
 
+HAS_USER_SITE = (site.USER_SITE is not None)
 OLD_SYS_PATH = None
 
 
@@ -195,6 +196,7 @@ def test_addsitedir(self):
     def test__getuserbase(self):
         self.assertEqual(site._getuserbase(), sysconfig._getuserbase())
 
+    @unittest.skipUnless(HAS_USER_SITE, 'need user site')
     def test_get_path(self):
         if sys.platform == 'darwin' and sys._framework:
             scheme = 'osx_framework_user'
@@ -244,6 +246,7 @@ def test_s_option(self):
         self.assertEqual(rc, 1,
                         "User base not set by PYTHONUSERBASE")
 
+    @unittest.skipUnless(HAS_USER_SITE, 'need user site')
     def test_getuserbase(self):
         site.USER_BASE = None
         user_base = site.getuserbase()
@@ -261,6 +264,7 @@ def test_getuserbase(self):
             self.assertTrue(site.getuserbase().startswith('xoxo'),
                             site.getuserbase())
 
+    @unittest.skipUnless(HAS_USER_SITE, 'need user site')
     def test_getusersitepackages(self):
         site.USER_SITE = None
         site.USER_BASE = None
@@ -295,6 +299,7 @@ def test_getsitepackages(self):
             wanted = os.path.join('xoxo', 'lib', 'site-packages')
             self.assertEqual(dirs[1], wanted)
 
+    @unittest.skipUnless(HAS_USER_SITE, 'need user site')
     def test_no_home_directory(self):
         # bpo-10496: getuserbase() and getusersitepackages() must not fail if
         # the current user has no home directory (if expanduser() returns the