A static-linked binary doesn't have a .dynamic section, but when starting ujail with -r or -w will automatically search for PT_DYNAMIC in ELF and exit with failure if it is not found. Fixes: #970 Signed-off-by: Yuteng Zhong <zonyitoo@qq.com> Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>