* gnu/packages/llvm.scm (llvm, clang-runtime, clang): Update to 3.8.1.
(llvm-3.7, clang-runtime-3.7, clang-3.7): New variables.
(clang-runtime-from-llvm)[arguments]: Disable tests, which were not
being run for previous versions anyhow but now fail hard.
(clang-from-llvm): Add #:patches keyword argument.
* gnu/packages/patches/clang-3.8-libc-search-path.patch: New patch.
* gnu/local.mk (dist_patch_DATA): Add it.
Co-authored-by: Dennis Mungai <dmngaie@gmail.scm>
