add hhvm workaround for https://github.com/facebook/hhvm/issues/5457
add hhvm workaround for https://github.com/facebook/hhvm/issues/5457

leafo/scssphp,webdevid/scssphp,leafo/scssphp,g105b/scssphp,g105b/scssphp,kkkyyy03/scssphp,dleffler/scssphp,g105b/scssphp,dleffler/scssphp,webdevid/scssphp,dleffler/scssphp,webdevid/scssphp,leafo/scssphp