gn: backport LFS64 cleanup

This is required to build with musl 1.2.4 and later.

pkgs/development/tools/build-managers/gn/generic.nix

@@ -1,4 +1,4 @@
-{ stdenv, lib, fetchgit, cctools, darwin, writeText
+{ stdenv, lib, fetchgit, fetchpatch, cctools, darwin, writeText
 , ninja, python3
 , ...
 }:
@@ -27,6 +27,15 @@ in stdenv.mkDerivation {
     inherit rev sha256;
   };
 
+  patches = [
+    (fetchpatch {
+      name = "LFS64.patch";
+      url = "https://gn.googlesource.com/gn/+/b5ff50936a726ff3c8d4dfe2a0ae120e6ce1350d%5E%21/?format=TEXT";
+      decode = "base64 -d";
+      hash = "sha256-/kh8t/Ip1EG2OIhydS//st/C80KJ4P31vGx7j8QpFh0=";
+    })
+  ];
+
   nativeBuildInputs = [ ninja python3 ];
   buildInputs = lib.optionals stdenv.isDarwin (with darwin; with apple_sdk.frameworks; [
     libobjc