pkg-repo: Follow symlinks and ignore directories starting with '.' or named 'Latest'.
This fixes running 'pkg repo' in a Poudriere-made directory that would result in several different versions of packages being added to the packagesite. Each of them would refer to some .real_* directory. Poudriere uses these directories to manage multiple previous builds and to have a "build in progress" directory that does not conflict with currently served packages. See also https://github.com/freebsd/poudriere/issues/293 See also Issue #1200