cli: drop extraneous daemon thread

it was only needed because we forked subdaemons and couldn't reuse the
main aio root. we now fork+exec, so the main aio root is always valid.

Change-Id: Ia19e20d52d65fe72721292be091f182a8a77a7cb

lix/nix/daemon.cc

@@ -286,8 +286,7 @@ static std::pair<TrustedFlag, std::string> authPeer(const PeerInfo & peer)
  * the client. Otherwise, decide based on the authentication settings
  * and user credentials (from the unix domain socket).
  */
-static void daemonLoop(AsyncIoRoot & aio, std::optional<TrustedFlag> forceTrustClientOpt);
-static void daemonLoopImpl(std::optional<TrustedFlag> forceTrustClientOpt)
+static void daemonLoop(AsyncIoRoot & aio, std::optional<TrustedFlag> forceTrustClientOpt)
 {
     if (chdir("/") == -1)
         throw SysError("cannot change current directory");
@@ -386,20 +385,6 @@ static void daemonLoopImpl(std::optional<TrustedFlag> forceTrustClientOpt)
         }
     }
 }
-static void daemonLoop(AsyncIoRoot & aio, std::optional<TrustedFlag> forceTrustClientOpt)
-{
-    // we can't reuse the external async io root since it'd be shared with the
-    // children we will create, potentially trashing state, but the *previous*
-    // root is still alive as far as kj is concerned. we cannot recreate it in
-    // the child easily because darwin closes kqueues after fork, and since kj
-    // asserts after the kqueue close returns EBADF we'll die. the least awful
-    // way around this is to run the daemon loop in its own thread, without an
-    // async io root, and thus not have any shared state after we have forked.
-    std::async(std::launch::async, [&] {
-        ReceiveInterrupts ri;
-        return daemonLoopImpl(forceTrustClientOpt);
-    }).get();
-}
 
 static void daemonInstance(AsyncIoRoot & aio, std::optional<TrustedFlag> forceTrustClientOpt)
 {