How do hiring committees for research positions view getting "scooped"?
I'm a little surprised by the implicit assumption that "scooped" ==> "no paper whatsoever." 

It's often possible--and desirable--to publish the scooped work anyway. It might have less impact than it otherwise would have, but it's miles better than nothing. Furthermore, it's unlikely that both papers tackle the problem exactly the same way; highlight those differences in your revised version. If nothing else, replications are increasingly appreciated. This is especially true in trendy areas, where both scooping and dubious, non-replicable results are most likely. 

It would be gauche for you to complain about this directly on your cover letter or CV (how would this even work?!). With a publication, however, your references can write: 


  "Grad Student's main project, characterizing the properties of
  l-Phlebotinum and d-Phlebotinum, was just accepted at the Journal of
  Decent Results. Although his thesis committee praised the work as a
  technical tour de force, it unfortunately attracted less attention
  than it might have after Evil et al. (2018) published similar
  results last December in Science."


Obviously, you'd prefer not to get scooped, but this does demonstrate that you're working on 'hot' problems that people do find interesting, which is better than nothing.