{forceLlvmCodegenBackend,ghcWithPackages}: update clang -fllvm logic

- The LLVM backend always needs an LLVM specific assembler, i.e. clang
  that ideally matches the version of LLVM actually used for codegen.

- The LLVM backend on Darwin requires some version of clang to be
  available. In light of LLVMAS, using a matching version seems to be
  best though this does risk messing with clang used for compiling C
  in the derivation.

  This mess can be avoided by compiling GHC with useLLVM = true which
  sets absolute paths in GHC's settings file. Due to closure size
  constraints, we can't really do that if NCG is available.

0 files changed, 0 insertions, 0 deletions