attr: patch to fix headers w/musl

pkgs/development/libraries/attr/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, gettext }:
+{ stdenv, fetchurl, gettext, targetPlatform }:
 
 stdenv.mkDerivation rec {
   name = "attr-2.4.47";
@@ -16,6 +16,8 @@ stdenv.mkDerivation rec {
 
   installTargets = "install install-lib install-dev";
 
+  patches = if (targetPlatform.libc == "musl") then [ ./fix-headers-musl.patch ] else null;
+
   meta = {
     homepage = http://savannah.nongnu.org/projects/attr/;
     description = "Library and tools for manipulating extended attributes";