brp: force all root-level directory permissions

Some distros, such as Arch Linux, make directories such as /bin a
symlink.  Without this patch, if distros like arch linux are at the top
priority some root-level items become symlinks and the user bypasses the
entire filesystem without the brc-wrap/exec-filter functionality.
installer: correct headers/linux confusion in output
brp: force exec-filter to always resolve symlinks

Otherwise symlinks in directories such as /applications will jump out of
the filesystem before they can be exec-filtered.