llvm 3.4 can't build shared libraries on Darwin due to rpath difficulties

[tel]

This might be better linked into NixOS/nixpkgs, but I'm currently testing it on this branch.

Right now, llvmGeneral requires shared libraries (I believe because it uses Template Haskell, which in turn requires GHCi, which in turn requires shared linking) but llvm itself is flagged to build on Darwin without shared libs. The relevant file is here.

If I adjust the flags to try building shared libs for Darwin it results in an LLVM compilation error. I have a log linked here. The short of it is the following however:

dyld: Library not loaded: libLLVMTableGen.dylib
  Referenced from: /private/var/folders/lj/655x29_s66718hvw6bdcvy1w0000gn/T/nix-build-llvm-3.4.2.drv-0/llvm/build/include/llvm/IR/../../../bin/llvm-tblgen
  Reason: image not found

This appears to be an rpath error, LLVM can't find its own compiled shared libraries in the nix tree.

Is there a fix for this in nix?