Fix the test_fcntl::test_posix_fallocate::success test with recent ZFS

POSIX 1003.1-2024 Issue 8 changed the error code for this operation, and
recent ZFS versions have followed suit.  So the test should accept
either the old error code (EINVAL) or the new one (ENOTSUP).

https://pubs.opengroup.org/onlinepubs/9799919799/functions/posix_fallocate.html

Author: asomers

test/test_fcntl.rs

@@ -541,13 +541,14 @@ mod test_posix_fallocate {
                 assert_eq!(tmp.read(&mut data).expect("read failure"), LEN);
                 assert_eq!(&data[..], &[0u8; LEN][..]);
             }
-            Err(Errno::EINVAL) => {
-                // POSIX requires posix_fallocate to return EINVAL both for
-                // invalid arguments (i.e. len < 0) and if the operation is not
-                // supported by the file system.
-                // There's no way to tell for sure whether the file system
-                // supports posix_fallocate, so we must pass the test if it
-                // returns EINVAL.
+            Err(Errno::ENOTSUP) | Err(Errno::EINVAL) => {
+                // POSIX 1003.1-2024 Issue 8 specified ENOTSUP for "the file
+                // system does not support this operation", so Nix should accept
+                // that error code and pass the test.
+                // But older POSIX required posix_fallocate to return EINVAL
+                // both for invalid arguments (i.e. len < 0) and if the
+                // operation is not supported by the file system.  So we must
+                // also pass the test if it returns EINVAL.
             }
             _ => res.unwrap(),
         }