nohup the server from GNU Emacs

main-command/src/main/scala/sbt/internal/client/NetworkClient.scala

@@ -337,8 +337,13 @@ class NetworkClient(
               List(DashDashDetachStdio, DashDashServer)
         }
 
+        // https://github.com/sbt/sbt/issues/6271
+        val nohup =
+          if (Util.isEmacs && !Util.isWindows) List("nohup")
+          else Nil
+
         val processBuilder =
-          new ProcessBuilder(cmd: _*)
+          new ProcessBuilder((nohup ++ cmd): _*)
             .directory(arguments.baseDirectory)
             .redirectInput(Redirect.PIPE)
         processBuilder.environment.put(Terminal.TERMINAL_PROPS, props)