Issue #7774: Set sys.executable to an empty string if argv[0] has been
set to an non existent program name and Python is unable to retrieve the real
program name.

Fix also sysconfig: if sys.executable is an empty string, use the current
working directory.
diff --git a/Misc/NEWS b/Misc/NEWS
index 8f450a9..a64bd16 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,10 @@
 Core and Builtins
 -----------------
 
+- Issue #7774: Set sys.executable to an empty string if argv[0] has been
+  set to an non existent program name and Python is unable to retrieve the real
+  program name
+
 - Issue #3137: Don't ignore errors at startup, especially a keyboard interrupt
   (SIGINT). If an error occurs while importing the site module, the error is
   printed and Python exits. Initialize the GIL before importing the site