merge-ort: ignore skip-worktree bit with virtual filesystem

Without this change, the mere conflicts start creating <path>~cruft
files on-disk, which is caught by the VFS for Git functional tests.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

merge-ort.c

@@ -4226,7 +4226,7 @@ static int record_conflicted_index_entries(struct merge_options *opt)
 			if (ce_skip_worktree(ce)) {
 				struct stat st;
 
-				if (!lstat(path, &st)) {
+				if (!core_virtualfilesystem && !lstat(path, &st)) {
 					char *new_name = unique_path(opt,
 								     path,
 								     "cruft");