local: Ignore additional errors for directory syncing

Apparently SMB/CIFS on Linux/macOS returns somewhat random errnos when
trying to sync a windows share which does not support calling fsync for
a directory.

changelog/unreleased/issue-3720

@@ -0,0 +1,13 @@
+Bugfix: Fix directory sync errors related repositories accessed via SMB
+
+On Linux and macOS accessing a repository via a SMB/CIFS mount resulted in
+restic failing to save the lock file:
+
+Save(<lock/071fe833f0>) returned error, retrying after 552.330144ms: sync /repo/locks: no such file or directory
+Save(<lock/bf789d7343>) returned error, retrying after 552.330144ms: sync /repo/locks: invalid argument
+
+This has been fixed by ignoring these error codes.
+
+https://github.com/restic/restic/issues/3720
+https://github.com/restic/restic/issues/3751
+https://github.com/restic/restic/pull/3752

internal/backend/local/local_unix.go

@@ -19,7 +19,7 @@ func fsyncDir(dir string) error {
 	}
 
 	err = d.Sync()
-	if errors.Is(err, syscall.ENOTSUP) {
+	if errors.Is(err, syscall.ENOTSUP) || errors.Is(err, syscall.ENOENT) || errors.Is(err, syscall.EINVAL) {
 		err = nil
 	}