Fix Darwin build

http://hydra.nixos.org/build/33279996

src/libstore/crypto.cc

@@ -37,10 +37,12 @@ SecretKey::SecretKey(const string & s)
 #endif
 }
 
+#if !HAVE_SODIUM
 [[noreturn]] static void noSodium()
 {
     throw Error("Nix was not compiled with libsodium, required for signed binary cache support");
 }
+#endif
 
 std::string SecretKey::signDetached(const std::string & data) const
 {

src/libstore/crypto.hh

@@ -39,7 +39,7 @@ struct PublicKey : Key
 private:
     PublicKey(const std::string & name, const std::string & key)
         : Key(name, key) { }
-    friend class SecretKey;
+    friend struct SecretKey;
 };
 
 typedef std::map<std::string, PublicKey> PublicKeys;

src/libstore/http-binary-cache-store.cc

@@ -48,7 +48,7 @@ protected:
         }
     }
 
-    void upsertFile(const std::string & path, const std::string & data)
+    void upsertFile(const std::string & path, const std::string & data) override
     {
         throw Error("uploading to an HTTP binary cache is not supported");
     }

src/libstore/nar-accessor.cc

@@ -33,7 +33,7 @@ struct NarIndexer : ParseSink, StringSource
     {
     }
 
-    void createDirectory(const Path & path)
+    void createDirectory(const Path & path) override
     {
         members.emplace(path,
             NarMember{FSAccessor::Type::tDirectory, false, 0, 0});
@@ -44,7 +44,7 @@ struct NarIndexer : ParseSink, StringSource
         currentPath = path;
     }
 
-    void isExecutable()
+    void isExecutable() override
     {
         isExec = true;
     }

src/libutil/ref.hh

@@ -2,6 +2,7 @@
 
 #include <memory>
 #include <exception>
+#include <stdexcept>
 
 namespace nix {
 

src/nix/legacy.hh

@@ -2,6 +2,7 @@
 
 #include <functional>
 #include <map>
+#include <string>
 
 namespace nix {