parse-sass: don't hardcode bash path
parse-sass: don't hardcode bash path

It's /bin/bash on some systems; just use /bin/sh instead.

https://bugzilla.gnome.org/show_bug.cgi?id=749593

jadahl/gtk,alexlarsson/gtk,Adamovskiy/gtk,davidgumberg/gtk,grubersjoe/adwaita,chergert/gtk,chergert/gtk,Adamovskiy/gtk,davidgumberg/gtk,Adamovskiy/gtk,jigpu/gtk,jigpu/gtk,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,jadahl/gtk,jadahl/gtk,davidgumberg/gtk,jadahl/gtk,jadahl/gtk,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,Adamovskiy/gtk,chergert/gtk,davidgumberg/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,Adamovskiy/gtk,Adamovskiy/gtk,chergert/gtk,jigpu/gtk,jigpu/gtk,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,chergert/gtk,chergert/gtk,alexlarsson/gtk,jadahl/gtk,alexlarsson/gtk,jadahl/gtk,Adamovskiy/gtk,jadahl/gtk,chergert/gtk,jigpu/gtk,grubersjoe/adwaita,davidgumberg/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk