Compiling .dts files out of tree

I’m making up an example where I need to compile a .dts file and want to do it out-of-tree so I don’t have to clone bb-overlays.

I’ve pulled together a Makefile[1] that seems to work, but is there a cleaner way to do this?

–Mark

[1] https://github.com/MarkAYoder/BeagleBoard-exercises/blob/master/displays/ili9341/tinyDRM/Makefile