libCEED using Hiprtc

[YohannDudouit]

It seems that Hip has JIT compilation now, the interface seems to be the same as nvrtc, thus it should be straightforward to port Cuda backends to Hip.
https://github.com/ROCm-Developer-Tools/HIP/blob/master/include/hip/hcc_detail/hiprtc.h

[jedbrown]

Yes, this file has actually been there since May, but it still isn't documented so I don't know how to interpret it. We talked with @noelchalmers and Damon at CEED3AM and they didn't seem to think it was operational yet. I'd recommend testing a simple case before investing significant time porting to an interface that may or may not work.