mark as standalone static libraries so they get placed into the correct directory on non-osx targets
standalone flag for mbgl-headless
Merge pull request #506 from mapbox/fix-linux-install

Mark libraries as standalone
refs #509: tickets good, inline TODO bad
Merge branch 'master' of github.com:mapbox/mapbox-gl-native
Merge branch 'master' into mbgl-config
add dummy mbgl-config generator script