tests/guest-debug: catch hanging guests

If gdb never actually connected with the guest we need to catch that
and clean-up after ourselves.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Message-Id: <20200513175134.19619-2-alex.bennee@linaro.org>

tests/guest-debug/run-test.py

@@ -80,4 +80,10 @@ if __name__ == '__main__':
         print("GDB crashed? SKIPPING")
         exit(0)
 
+    try:
+        inferior.wait(2)
+    except subprocess.TimeoutExpired:
+        print("GDB never connected? Killed guest")
+        inferior.kill()
+
     exit(result)