ostbuild: Don't check for a "Makefile"
ostbuild: Don't check for a "Makefile"

WebKit uses GNUmakefile which is totally valid, and this check
isn't really gaining us anything.

GNOME/ostree,sujitfulse/ostree,leandrosansilva/ostree,GNOME/ostree,resin-io/ostree,resin-io/ostree,leandrosansilva/ostree,sujitfulse/ostree,resin-io/ostree,sujitfulse/ostree,gatispaeglis/ostree,gatispaeglis/ostree,sujitfulse/ostree,sujitfulse/ostree,gatispaeglis/ostree,resin-io/ostree,resin-io/ostree,leandrosansilva/ostree,leandrosansilva/ostree,GNOME/ostree,GNOME/ostree,leandrosansilva/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,GNOME/ostree