runtime(doc): mention the "pipefail" shell option

related: #17787

Signed-off-by: Christian Brabandt <[email protected]>

Author: chrisbra

runtime/doc/options.txt

@@ -7503,6 +7503,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 	Don't forget to precede the space with a backslash: ":set sp=\ ".
 	In the future pipes may be used for filtering and this option will
 	become obsolete (at least for Unix).
+	Note: When using a pipe like "| tee", you'll lose the exit code of the
+	shell command.  This might be configurable by your shell, look for
+	the pipefail option (for bash and zsh, use ":set -o pipefail").
 	This option cannot be set from a |modeline| or in the |sandbox|, for
 	security reasons.