Shell: Avoid waiting for jobs that were *just* unblocked

This fixes the issue with C-z not suspending the job on the first try.
...and further signal issues when the suspended job is contiued.

Shell/Builtin.cpp

@@ -93,6 +93,7 @@ int Shell::builtin_bg(int argc, const char** argv)
  }
 
  job->set_running_in_background(true);
+ job->set_is_suspended(false);
 
  dbg() << "Resuming " << job->pid() << " (" << job->cmd() << ")";
  fprintf(stderr, "Resuming job %" PRIu64 " - %s\n", job->job_id(), job->cmd().characters());
@@ -339,6 +340,7 @@ int Shell::builtin_fg(int argc, const char** argv)
  }
 
  job->set_running_in_background(false);
+ job->set_is_suspended(false);
 
  dbg() << "Resuming " << job->pid() << " (" << job->cmd() << ")";
  fprintf(stderr, "Resuming job %" PRIu64 " - %s\n", job->job_id(), job->cmd().characters());

Shell/Job.h

@@ -75,6 +75,7 @@ class Job : public RefCounted<Job> {
  bool should_be_disowned() const { return m_should_be_disowned; }
  void disown() { m_should_be_disowned = true; }
  bool is_running_in_background() const { return m_running_in_background; }
+ bool is_suspended() const { return m_is_suspended; }
  void unblock() const
  {
  if (!m_exited && on_exit)
@@ -94,6 +95,8 @@ class Job : public RefCounted<Job> {
  on_exit(*this);
  }
 
+ void set_is_suspended(bool value) const { m_is_suspended = value; }
+
  void set_running_in_background(bool running_in_background)
  {
  m_running_in_background = running_in_background;
@@ -111,5 +114,6 @@ class Job : public RefCounted<Job> {
  int m_exit_code { -1 };
  Core::ElapsedTimer m_command_timer;
  mutable bool m_active { true };
+ mutable bool m_is_suspended { false };
  bool m_should_be_disowned { false };
 };

Shell/Shell.cpp

@@ -561,16 +561,18 @@ Vector<RefPtr<Job>> Shell::run_commands(Vector<AST::Command>& commands)
  }
 #endif
  auto job = run_command(command);
+ if (!job)
+ continue;
 
  if (command.should_wait) {
  block_on_job(job);
- jobs_to_wait_for.append(job);
+ if (!job->is_suspended())
+ jobs_to_wait_for.append(job);
  } else {
  if (command.is_pipe_source) {
  jobs_to_wait_for.append(job);
  } else if (command.should_notify_if_in_background) {
- if (job)
- job->set_running_in_background(true);
+ job->set_running_in_background(true);
  restore_stdin();
  }
  }

Shell/main.cpp

@@ -121,8 +121,10 @@ int main(int argc, char** argv)
  Core::EventLoop::register_signal(SIGTSTP, [](auto) {
  auto job = s_shell->current_job();
  s_shell->kill_job(job, SIGTSTP);
- if (job)
+ if (job) {
+ job->set_is_suspended(true);
  job->unblock();
+ }
  });
 
 #ifndef __serenity__