erofs-utils: fix distcheck target

Fix the broken distcheck target [1], and it needs to be
resolved independently first.

[1] https://lore.kernel.org/r/20210121163715.10660-5-sehuww@mail.scut.edu.cn

Link: https://lore.kernel.org/r/20210513041311.22480-1-xiang@kernel.org
Reported-by: Hu Weiwen <sehuww@mail.scut.edu.cn>
Signed-off-by: Gao Xiang <xiang@kernel.org>
1 file changed