ssh-ng: Don't set CPU affinity on the remote

Fixes #3138.

src/libstore/remote-store.cc

@@ -151,7 +151,7 @@ void RemoteStore::initConnection(Connection & conn)
         conn.to << PROTOCOL_VERSION;
 
         if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 14) {
-            int cpu = settings.lockCPU ? lockToCurrentCPU() : -1;
+            int cpu = sameMachine() && settings.lockCPU ? lockToCurrentCPU() : -1;
             if (cpu != -1)
                 conn.to << 1 << cpu;
             else

src/libstore/remote-store.hh

@@ -29,6 +29,8 @@ public:
     const Setting<unsigned int> maxConnectionAge{(Store*) this, std::numeric_limits<unsigned int>::max(),
             "max-connection-age", "number of seconds to reuse a connection"};
 
+    virtual bool sameMachine() = 0;
+
     RemoteStore(const Params & params);
 
     /* Implementations of abstract store API methods. */
@@ -146,6 +148,9 @@ public:
 
     std::string getUri() override;
 
+    bool sameMachine()
+    { return true; }
+
 private:
 
     ref<RemoteStore::Connection> openConnection() override;

src/libstore/ssh-store.cc

@@ -35,6 +35,9 @@ public:
         return uriScheme + host;
     }
 
+    bool sameMachine()
+    { return false; }
+
     void narFromPath(const Path & path, Sink & sink) override;
 
     ref<FSAccessor> getFSAccessor() override;