bug#72547: [PATCH 5/9] tests: Skip mkdtemp test for invalid template on Darwin.

Darwin accepts any template, as demonstrated here:

    #include <stdio.h>
    #include <unistd.h>

    int
    main(void)
    {
    	char template[] = {'T', '-', 'A', 'A', 'A', 'A', 'A', 'A', '\0'};
    	char *res = mkdtemp(template);
    	puts(res ? res : "(null)");
    	perror("mkdtemp");
    }

Outputs:

    T-AAAAAA
    mkdtemp: Undefined error: 0

This does not match prescribed POSIX behavior, but it is what it is.

* test-suite/tests/filesys.test (skip-on-darwin): New procedure.
("mkdtemp")["invalid template"]: Skip on Darwin.
---
 test-suite/tests/filesys.test | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test-suite/tests/filesys.test b/test-suite/tests/filesys.test
index fa8d6f797..72d778145 100644
--- a/test-suite/tests/filesys.test
+++ b/test-suite/tests/filesys.test
@@ -34,6 +34,9 @@
 (define (test-directory2)
   (data-file-name "filesys-test-dir2.tmp"))
 
+(define (skip-on-darwin)
+  (when (string-ci=? "darwin" (vector-ref (uname) 0))
+    (throw 'untested)))
 
 ;;;
 ;;; copy-file
@@ -345,6 +348,8 @@
            (= (string-length name) 8)))))
 
   (pass-if-exception "invalid template" exception:system-error
+    ;; MacOS accepts any template and just does no replacements.
+    (skip-on-darwin)
     (if (not (defined? 'mkdtemp))
         (throw 'unresolved)
         (mkdtemp "T-AAAAAA")))
-- 
2.45.2