Ports over dfsan from polytracker-llvm

[surovic]

The ports over the DataflowSanitizer pass and related parts of compiler-rt from our modified fork of the LLVM repository. By doing this we are no longer dependent on that fork and can eventually move to more recent versions of LLVM. For this to happen, parts of polytracker's CMake build system had to be modified and the Dockerfile had to be rewritten. Users should also expect increased docker image build times as we now build libc++, which was part of the polytracker-llvm docker dependency build. The sum duration of polytracker-llvm and polytracker docker image build has however been drastically lowered. Future hope is to optimize the docker image build further.

[kaoudis]

Thanks for updating the gllvm! I may have missed it, but what golang version is supported in this new Dockerfile version? I think the current master Polytracker base Dockerfile is pinned to an old Golang, so am curious whether we are using Jammy's default golang or otherwise replace/configure it in some way I haven't noticed yet here.

[surovic]

root@dea90b62fec0:/workdir# go version 
go version go1.18.1 linux/amd64

I think we're using the Jammy default. Which is also the same we've used in polytracker-llvm unless I'm missing something.

[surovic]

Is it recorded somewhere what version of the compiler-rt that is included here? I think it would be good to add that information somewhere.

I'll make an issue to add a note in a new polytracker/src/compiler-rt/README.md.

I've assumed that anything in compiler-rt is untouched so I haven't paid to much attention to those files. Is that correct?

Yes. That is correct.