Revert "Mac: activate homebrew if available"

if [ "$(uname)" = "Darwin" ]; then

  PLATFORM=MacOSX

  if test -d /usr/local/opt/curl/bin; then

    # That's where homebrew lives, and it has the curl that doesn't cause

    # cert errors from the OS being too old.

    export PATH="/usr/local/opt/curl/bin:$PATH"

  fi

else

  PLATFORM=Linux

fi