macOS 10.12.6 AMD Radeon R9 M390 2048 MB
Downloaded from https://builder.blender.org/download/
All working versions of 2.8 have shown this for me, on 10.12.5 and 10.12.6, In Evee and Clay the grid is an opaque 'floor' and appears to be very large.
Exact steps for others to reproduce the error
Just load the build and observe the cube in the default scene