[PATCH] [clang] cmake: resolve symlinks in ClangConfig.cmake

[PATCH] [clang] cmake: resolve symlinks in ClangConfig.cmake

Ensure that symlinks such as /usr/lib/cmake/clang-X.Y (pointing to
/usr/lib/llvm-X.Y/lib/cmake/llvm) are resolved. This ensures that
CLANG_INSTALL_PREFIX ends up to be /usr/lib/llvm-X.Y instead of /usr.

Partially addresses PR37128

Gbp-Pq: Name 0001-tools-clang-cmake-resolve-symlinks-in-ClangConfig.cmake.patch