Disable OpenEXR support on Ubuntu
The OpenEXR format (.exr) isn't very useful on GNOME-ish desktops without a gdk-pixbuf loader. This provides a gdk-pixbuf loader but it isn't packaged in Debian yet: https://github.com/afichet/openexr-thumbnailer
openexr would also require Ubuntu main inclusion review. See https://launchpad.net/bugs/2070882 and https://github.com/canonical/ubuntu-mir