Help on custom bike build please

Hi there, 

I am in the process of building a bike for commuting. It’s a flat bar as I went for SLX hydraulic brakes, the other option was the SRAM Rival Hydraulics which was far too expensive for me. 

I’ve also got a SRAM Rival 1×11 Crankset 50t as I’ve never been a fan of front derailleurs and the simplicity appealed to me.

This is running on a Charge Plug 5 steel frame.

My choices as I can see now are:

Shimano Deore XT 1×11 rear derailleur and Cassette, I assume they’d work fine with the SRAM crankset as they were designed to work with a single chainring – and use the XT shifter also. This is what I’m most inclined to do.

My other option is to go SRAM 1×11 Cassette and rear derailleur. But I’m not sure what shifter to go for, I’m guessing the SRAM GX shifter should work but not totally sure. I’d have to get a Problem Solvers Mismatch mount though.

Any advice on other options regarding shifters etc would be really appreciated!