bug#63865: 29.0.90; call-process while owning the X selection hangs other processes

[Spencer Baugh]

BTW, the buggy behavior in Slack at least can be fixed by running:

slack 'slack://setting/?update={"isClipboardReadDisabled":true}'

then Slack won't constantly try to read the clipboard in the background.
(Apparently this may be fixed in the future, future readers should check
with Slack)

Though, I'm still of the opinion that we should make a
call-process-with-lisp which doesn't stop Lisp from running while
call-process-with-lisp is running, and use that everywhere.  Then we
wouldn't be triggering such bugs...