Fix clang build failure

Apparently opinion is divided on whether [[noreturn]] is allowed on a
lambda: http://stackoverflow.com/questions/26888805/how-to-declare-a-lambdas-operator-as-noreturn

http://hydra.nixos.org/build/36462100

release.nix

@@ -99,6 +99,8 @@ let
 
         doInstallCheck = true;
         installCheckFlags = "sysconfdir=$(out)/etc";
+
+        stdenv = clangStdenv;
       });
 
 

src/libstore/nar-info.cc

@@ -5,7 +5,7 @@ namespace nix {
 
 NarInfo::NarInfo(const std::string & s, const std::string & whence)
 {
-    auto corrupt = [&]() [[noreturn]] {
+    auto corrupt = [&]() {
         throw Error("NAR info file ‘%1%’ is corrupt");
     };
 
@@ -14,6 +14,7 @@ NarInfo::NarInfo(const std::string & s, const std::string & whence)
             return parseHash(s);
         } catch (BadHash &) {
             corrupt();
+            return Hash(); // never reached
         }
     };