Actually conditionally include liquid-c (#7792)
Actually conditionally include liquid-c (#7792)

Merge pull request 7792
ryanshaw/jekyll,jekyll/jekyll,x-way/jekyll,jekyll/jekyll,fulldecent/jekyll,tillgrallert/jekyll,fulldecent/jekyll,jaybe-jekyll/jekyll,jekyll/jekyll,ryanshaw/jekyll,tillgrallert/jekyll,jaybe-jekyll/jekyll,ryanshaw/jekyll,yhironaka/yhironaka.github.io,chrisfinazzo/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,chrisfinazzo/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,fulldecent/jekyll,fulldecent/jekyll,x-way/jekyll,tillgrallert/jekyll,jekyll/jekyll