llvmPackages_13: Copy from llvmPackages_git

(cherry picked from commit f3f86d47220e2c2332d60f6bd0a89b76a628529d)

pkgs/development/compilers/llvm/13/libcxx/default.nix

@@ -0,0 +1,51 @@
+{ lib, stdenv, llvm_meta, src, cmake, python3, fixDarwinDylibNames, version
+, enableShared ? !stdenv.hostPlatform.isStatic
+}:
+
+stdenv.mkDerivation rec {
+  pname = "libcxx";
+  inherit version;
+
+  inherit src;
+  sourceRoot = "source/${pname}";
+
+  outputs = [ "out" "dev" ];
+
+  patches = [
+    ./gnu-install-dirs.patch
+  ] ++ lib.optionals stdenv.hostPlatform.isMusl [
+    ../../libcxx-0001-musl-hacks.patch
+  ];
+
+  preConfigure = lib.optionalString stdenv.hostPlatform.isMusl ''
+    patchShebangs utils/cat_files.py
+  '';
+
+  nativeBuildInputs = [ cmake python3 ]
+    ++ lib.optional stdenv.isDarwin fixDarwinDylibNames;
+
+  cmakeFlags = [
+  ] ++ lib.optional (stdenv.hostPlatform.isMusl || stdenv.hostPlatform.isWasi) "-DLIBCXX_HAS_MUSL_LIBC=1"
+    ++ lib.optional (stdenv.hostPlatform.useLLVM or false) "-DLIBCXX_USE_COMPILER_RT=ON"
+    ++ lib.optional stdenv.hostPlatform.isWasm [
+      "-DLIBCXX_ENABLE_THREADS=OFF"
+      "-DLIBCXX_ENABLE_FILESYSTEM=OFF"
+      "-DLIBCXX_ENABLE_EXCEPTIONS=OFF"
+    ] ++ lib.optional (!enableShared) "-DLIBCXX_ENABLE_SHARED=OFF";
+
+  passthru = {
+    isLLVM = true;
+  };
+
+  meta = llvm_meta // {
+    homepage = "https://libcxx.llvm.org/";
+    description = "C++ standard library";
+    longDescription = ''
+      libc++ is an implementation of the C++ standard library, targeting C++11,
+      C++14 and above.
+    '';
+    # "All of the code in libc++ is dual licensed under the MIT license and the
+    # UIUC License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
+  };
+}