llvm: 3.7.1 -> 3.8.0 (close #13801)
vcunat's review:
- let's not switch the default versions of llvm* for now
- the only changes I see is adding python to clang's buildInputs
and using the big so-file as discussed in #12759
(BUILD_SHARED_LIBS -> LLVM_LINK_LLVM_DYLIB)
- in future it will be nice to split libLLVM into a separate output
authored by Andrew Kelley and committed by Vladimír Čunát f5fe051c 58a65c01