bug#72547: [PATCH 6/9] tests: Fix spawn with #:environment on MacOS.

MacOS adds __CF_USER_TEXT_ENCODING to every program, in similar way GNU
Hurd prepends LD_ORIGIN_PATH (based on the comment).  So extend the
logic to do similar stripping on MacOS.

* test-suite/tests/posix.test ("spawn")
["env with #:environment and #:output"]: Strip trailing
__CF_USER_TEXT_ENCODING environment variable when on Darwin.
---
 test-suite/tests/posix.test | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/test-suite/tests/posix.test b/test-suite/tests/posix.test
index 18dad8902..ac5a3b289 100644
--- a/test-suite/tests/posix.test
+++ b/test-suite/tests/posix.test
@@ -442,12 +442,23 @@
         (close-port (car input+output))
         (waitpid pid)
 
-        ;; On GNU/Hurd, the exec server prepends 'LD_ORIGIN_PATH' for
-        ;; every program: <https://bugs.gnu.org/62501>.  Strip it.
-        (if (and (string=? "GNU" (utsname:sysname (uname)))
-                 (string-prefix? "LD_ORIGIN_PATH=" str))
-            (string-drop str (+ 1 (string-index str #\newline)))
-            str))))
+        (let ((sysname (utsname:sysname (uname))))
+          (cond
+           ((string=? "GNU" sysname)
+            ;; On GNU/Hurd, the exec server prepends 'LD_ORIGIN_PATH' for
+            ;; every program: <https://bugs.gnu.org/62501>.  Strip it.
+            (if (string-prefix? "LD_ORIGIN_PATH=" str)
+                (string-drop str (+ 1 (string-index str #\newline)))
+                str))
+           ((string-ci=? "darwin" sysname)
+            ;; MacOS appends '__CF_USER_TEXT_ENCODING' for every program.  Strip
+            ;; it.
+            (let ((pos (string-contains str "__CF_USER_TEXT_ENCODING=")))
+              (if pos
+                  (string-drop-right str (- (string-length str) pos))
+                  str)))
+           (else
+            str))))))
 
   (pass-if-equal "ls /proc/self/fd"
       "0\n1\n2\n3\n"                     ;fourth FD is for /proc/self/fd
-- 
2.45.2