Shell: Moves pipelined processes to one process group

Author: https://github.com/alimpfard
Commit: ab3e787334
Pull-request: https://github.com/SerenityOS/serenity/pull/3085
Reviewed-by: https://github.com/BenWiederhake

Shell/Job.cpp

@@ -25,6 +25,7 @@
  */
 
 #include "Job.h"
+#include "AST.h"
 #include <inttypes.h>
 #include <stdio.h>
 #include <sys/wait.h>