The ms-holographic-experimental branch is very dated at this point and cannot be built with current tooling (VS2017).
I was able to build this version with VS2017: https://github.com/mlfarrell/angle
When can we expect this branch to catch up? It is still referencing Windows 8.1 components. Should we assume this branch will not be supported by Microsoft? It would help to get some sort of statement around this. No support from Microsoft is ok, at least then the community can move on. Having the branch sit here implies it might be updated.