bug#43364: Possible bug with output redirection

Dear guilers,

When using with-output-to-string, the output of external processes
started using system* and the like is not redirected to the temporary
port. As far as I can tell, it just redirects things written/displayed
from within guile.
This seems to be a bug, or if this is intended behaviour it might be
beneficial to document this somewhere.

As an example:
I'd expect snippet [0] to behave like snippet [1] and return "bar",
instead it just returns the empty string.

This probably affects other similar functions.

Pandemically,
pinoaffe

[0]:
(with-output-to-string
 (lambda ()
   (system* "echo" "bar")))

[1]:
(with-output-to-string
 (lambda ()
   (display "bar")))