erofs-utils: fix `Not a directory` error for incremental builds
If an incremental layer contains a directory but the same path in
the base layer is a non-directory, it will fail unexpectedly.
Fix it now.
Reported-by: Hongzhen Luo <hongzhen@linux.alibaba.com>
Co-developped-by: Hongzhen Luo <hongzhen@linux.alibaba.com>
Fixes: f64d9d02576b ("erofs-utils: introduce incremental builds")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241122075659.2869515-1-hsiangkao@linux.alibaba.com