* gnu/packages/llvm.scm (llvm-10, clang-runtime-10, clang-10) (clang-toolchain-10, llvm-9, clang-runtime-9, clang-9) (clang-toolchain-9): New variables. (llvm, clang, clang-runtime, clang-toolchain): Redefine as aliases to the '-9' bindings. * gnu/packages/patches/clang-10.0-libc-search-path.patch: New file. * gnu/local.mk (dist_patch_DATA): Add it.