Before generating the factory image, check if the input file exists. Fix the build error when sysupgrade image is too big: [mkwrgimg] *** error: stat failed on /builder/shared-workdir/build/build_dir/target-mipsel_24kc_musl/linux-ramips_rt288x/tmp/openwrt-ramips-rt288x-airlink101_ar670w-squashfs-factory.bin, No such file or directory Signed-off-by: Shiji Yang <yangshiji66@outlook.com> Link: https://github.com/openwrt/openwrt/pull/18836 Signed-off-by: Robert Marko <robimarko@gmail.com>