* gnu/packages/patches/clang-libc-search-path.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/llvm.scm (clang-from-llvm)[source]: Use it.
[inputs]: Add "gcc-lib".
[arguments]. Add -DGCC_INSTALL_PREFIX and -DC_INCLUDE_DIRS to
#:configure-flags. Add #:phases argument.
