sandbox: Add file-write-setugid for macOS 10.13
sandbox: Add file-write-setugid for macOS 10.13

On macOS 10.13 High Sierra, file-write* does not seem to include
file-write-setugid, therefore adding it explicitly to allow build
scripts to produce suid/sgid binaries.

Closes: https://trac.macports.org/ticket/54963

macports/macports-base,macports/macports-base,danchr/macports-base,neverpanic/macports-base,neverpanic/macports-base,danchr/macports-base