Shell: Stop a for loop upon receiving two consecutive interruptions

This does not work perfectly (just like every other shell...), if the
running program handles the signal (SIGINT in this case) and quits
cleanly, the shell cannot detect the interruption.
This is the case with our `sleep(1)`.

Shell/AST.cpp

@@ -30,6 +30,7 @@
 #include <AK/StringBuilder.h>
 #include <AK/URL.h>
 #include <LibCore/File.h>
+#include <signal.h>
 
 //#define EXECUTE_DEBUG
 
@@ -754,6 +755,8 @@ RefPtr<Value> ForLoop::run(RefPtr<Shell> shell)
     if (!m_block)
         return create<ListValue>({});
 
+    size_t consecutive_interruptions = 0;
+
     NonnullRefPtrVector<Value> values;
     auto resolved = m_iterated_expression->run(shell)->resolve_without_cast(shell);
     if (resolved->is_list_without_resolution())
@@ -762,6 +765,9 @@ RefPtr<Value> ForLoop::run(RefPtr<Shell> shell)
         values = create<ListValue>(resolved->resolve_as_list(shell))->values();
 
     for (auto& value : values) {
+        if (consecutive_interruptions == 2)
+            break;
+
         auto frame = shell->push_frame();
         shell->set_local_variable(m_variable_name, value);
 
@@ -771,6 +777,13 @@ RefPtr<Value> ForLoop::run(RefPtr<Shell> shell)
             if (!job || job->is_running_in_background())
                 continue;
             shell->block_on_job(job);
+            if (job->signaled()
+                && (job->termination_signal() == SIGINT
+                    || job->termination_signal() == SIGKILL
+                    || job->termination_signal() == SIGQUIT))
+                ++consecutive_interruptions;
+            else
+                consecutive_interruptions = 0;
         }
     }