Index: Lib/sysconfig.py
===================================================================
--- Lib/sysconfig.py	(revision 78833)
+++ Lib/sysconfig.py	(working copy)
@@ -84,7 +84,10 @@
 _EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
 _CONFIG_VARS = None
 _USER_BASE = None
-_PROJECT_BASE = os.path.dirname(realpath(sys.executable))
+# Note: sys.executable can be '' or even a directory, until #7774 is fixed.
+_PROJECT_BASE = realpath(sys.executable)
+if not os.path.isdir(_PROJECT_BASE):
+    _PROJECT_BASE = os.path.dirname(_PROJECT_BASE)
 
 if os.name == "nt" and "pcbuild" in _PROJECT_BASE[-8:].lower():
     _PROJECT_BASE = realpath(os.path.join(_PROJECT_BASE, pardir))