tests: Port sysroot.js away from libgsystem
tests: Port sysroot.js away from libgsystem

My case-sensitive `git grep` didn't find this one originally,
but the Travis+Debian setup was configured to run it.

Closes: #451
Approved by: jlebon

gatispaeglis/ostree,GNOME/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree