* gnu/packages/llvm.scm (clang-runtime-from-llvm)[native-inputs]: When
building clang-runtime-18 or newer use gcc-13.
(%llvm-monorepo-hashes): Add entry for llvm-18.
(%llvm-patches): Add entry for llvm-18.
(llvm-18, clang-runtime-18, clang-18, libomp-18, clang-toolchain-18):
New variables.
* gnu/packages/patches/clang-18.0-libc-search-path.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
Change-Id: I4027065398300104c6a310187007448f5b2780c1
