Fix hang in build-remote

Author: edolstra

src/build-remote/build-remote.cc

@@ -241,7 +241,7 @@ int main (int argc, char * * argv)
 
         if (!missing.empty()) {
             Activity act(*logger, lvlTalkative, actUnknown, fmt("copying outputs from '%s'", storeUri));
-            setenv("NIX_HELD_LOCKS", concatStringsSep(" ", missing).c_str(), 1); /* FIXME: ugly */
+            store->locksHeld.insert(missing.begin(), missing.end()); /* FIXME: ugly */
             copyPaths(ref<Store>(sshStore), store, missing, NoRepair, NoCheckSigs, substitute);
         }
 

src/libstore/local-store.cc

@@ -992,7 +992,6 @@ void LocalStore::addToStore(const ValidPathInfo & info, const ref<std::string> &
         /* Lock the output path.  But don't lock if we're being called
            from a build hook (whose parent process already acquired a
            lock on this path). */
-        static auto locksHeld = tokenizeString<PathSet>(getEnv("NIX_HELD_LOCKS"));
         if (!locksHeld.count(info.path))
             outputLock.lockPaths({realPath});
 

src/libstore/local-store.hh

@@ -104,6 +104,9 @@ private:
 
 public:
 
+    // Hack for build-remote.cc.
+    PathSet locksHeld = tokenizeString<PathSet>(getEnv("NIX_HELD_LOCKS"));
+
     /* Initialise the local store, upgrading the schema if
        necessary. */
     LocalStore(const Params & params);