In vkd3d (from wine), I think you have a DXIL->SPIR-V translater (much more robust than any high level shading language converter since it is a much more simple intermediate language).
That said, apart from this abomination of llvm, is there a HLSL->DXIL compiler written in plain and simple C99 (namely which require NOT gcc or clang to compile)?
Also to answer your question, no. The hlsl to dxil translation is basically owned by microsoft. There's been little effort to move away from that