Tramp currently isn't able to handle this, so the result will just
produce an error (bug#61024).
* lisp/eshell/esh-proc.el (eshell-gather-process-output): Check for a
remote 'default-directory' before trying to make a pipe process.
* test/lisp/eshell/esh-proc-tests.el
(esh-var-test/output/remote-redirect): New test.