Forbid basename(3) and dirname(3)

There are at least two interpretations of basename(3),
in addition to both functions being allowed to /both/ return a static
buffer (unsuitable in multi-threaded environments) /and/ raze the input
(which encourages overallocations, at best)

Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12105

lib/libzfs/libzfs_pool.c

@@ -4309,7 +4309,7 @@ zfs_save_arguments(int argc, char **argv, char *string, int len)
 {
 	int i;
 
-	(void) strlcpy(string, basename(argv[0]), len);
+	(void) strlcpy(string, zfs_basename(argv[0]), len);
 	for (i = 1; i < argc; i++) {
 		(void) strlcat(string, " ", len);
 		(void) strlcat(string, argv[i], len);