clang-3.5: fix build

Make Obj public in llvm's IntrusiveRefCntPtr

This fixes NixOs/nixpkgs#15974

It's not a nice fix, as it's really clang's problem. The proper fix
should modify clang's usage of IntrusiveRefCntPtr.

pkgs/development/compilers/llvm/3.5/clang.nix

@@ -50,6 +50,5 @@ in stdenv.mkDerivation {
     homepage    = http://llvm.org/;
     license     = stdenv.lib.licenses.bsd3;
     platforms   = stdenv.lib.platforms.all;
-    broken      = true;
   };
 }

pkgs/development/compilers/llvm/3.5/fix-15974.patch

@@ -0,0 +1,15 @@
+diff --git a/include/llvm/ADT/IntrusiveRefCntPtr.h b/include/llvm/ADT/IntrusiveRefCntPtr.h
+index f9df378..9d860ec 100644
+--- a/include/llvm/ADT/IntrusiveRefCntPtr.h
++++ b/include/llvm/ADT/IntrusiveRefCntPtr.h
+@@ -134,9 +134,9 @@ public:
+ //===----------------------------------------------------------------------===//
+   template <typename T>
+   class IntrusiveRefCntPtr {
++  public:
+     T* Obj;
+ 
+-  public:
+     typedef T element_type;
+ 
+     explicit IntrusiveRefCntPtr() : Obj(nullptr) {}

pkgs/development/compilers/llvm/3.5/llvm.nix

@@ -53,6 +53,8 @@ in stdenv.mkDerivation rec {
     "-DCAN_TARGET_i386=false"
   ];
 
+  patches = [ ./fix-15974.patch ];
+
   postBuild = ''
     rm -fR $out
 
@@ -75,3 +77,4 @@ in stdenv.mkDerivation rec {
     platforms   = stdenv.lib.platforms.all;
   };
 }
+