bpo-45506: Go back to not running most of test_embed in out-of-tree builds. (gh-29063)

In gh-28954 I adjusted how test_embed determines if it should be skipped. That broke out-of-tree builds. This change fixes them.

https://bugs.python.org/issue45506

Author: ericsnowcurrently

Diff for: Lib/test/test_embed.py

@@ -61,7 +61,7 @@ def setUp(self):
         else:
             exepath = os.path.join(builddir, 'Programs')
         self.test_exe = exe = os.path.join(exepath, exename)
-        if not os.path.exists(exe):
+        if exepath != support.REPO_ROOT or not os.path.exists(exe):
             self.skipTest("%r doesn't exist" % exe)
         # This is needed otherwise we get a fatal error:
         # "Py_Initialize: Unable to get the locale encoding