llvmPackages_12: Improve and extend the meta attributes

pkgs/development/compilers/llvm/12/libunwind/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, version, fetch, libcxx, llvm, cmake
+{ lib, stdenv, llvm_meta, version, fetch, libcxx, llvm, cmake
 , enableShared ? !stdenv.hostPlatform.isStatic
 }:
 
@@ -18,4 +18,16 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ cmake ];
 
   cmakeFlags = lib.optional (!enableShared) "-DLIBUNWIND_ENABLE_SHARED=OFF";
+
+  meta = llvm_meta // {
+    # Details: https://github.com/llvm/llvm-project/blob/main/libunwind/docs/index.rst
+    homepage = "https://clang.llvm.org/docs/Toolchain.html#unwind-library";
+    description = "LLVM's unwinder library";
+    longDescription = ''
+      The unwind library provides a family of _Unwind_* functions implementing
+      the language-neutral stack unwinding portion of the Itanium C++ ABI (Level
+      I). It is a dependency of the C++ ABI library, and sometimes is a
+      dependency of other runtimes.
+    '';
+  };
 }