How can I install gutters where there is no roof overhang, and the walls are concrete block?

I have a detached garage that has a flat rubber roof that slopes from front to back. There is however no overhang at the back of the garage, and no gutters, so water is running down the concrete block walls.

Question: What is the best way to install it? Should I get a piece of pressure treated wood and attach that to the block first, and then attach the gutter to the wood?