bug#64216: Proc open-input-pipe returns #eof when reading on macOS, works as expected on Linux

[Jose Ortiz]

When reading from open-input-pipe, it returns #eof on macOS devices, while it 
works properly in Linux.
```
(use-modules (ice-9 popen)
             (ice-9 rdelim))
(let* ((port (open-input-pipe "date --utc"))
       (str  (read-line port)))
  (close-pipe port)
  str)
```
macOS> #<eof>
linux> "Thu Jun 22 12:30:26 AM UTC 2023"


Building latest and running popen.test also fails with:

m1 :: Projects/guile/test-suite ? guile -L . -e main -s guile-test 
tests/popen.test
Running tests/popen.test
                                                                                                                                                                  
FAIL: tests/popen.test: open-input-pipe: echo hello
FAIL: tests/popen.test: open-input-pipe: open-input-pipe process gets 
(current-input-port) as stdin
ERROR: tests/popen.test: open-output-pipe: no duplicate - arguments: ((wrong-type-arg 
"string-append" "Wro
ng type (expecting ~A): ~S" ("string" #f) (#f)))



- Jose