Report the filename in the FILE column correctly when using the --dir opion

Hi, I noticed that when using `--dir`, find which seems to be used to report the path of the file is not working properly:

    RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH      FILE
    No RELRO        No canary found   NX enabled    Not an ELF file   No RPATH   No RUNPATH   find: `path/to/some/file': No such file or directory

It seems this is because when run as follows:

    path/to/checksec.sh --dir path/to/some

the script will first cd into `path/to/some` before scanning, but then was prepending `path/to/some` to the file as well