Use action graph cache for `buck targets --show-output`
Use action graph cache for `buck targets --show-output`

Summary: I noticed `buck targets --show-output` was slow after I'd just done a build of that target, and it looks like it's recomputing the action graph.  Is it valid to just grab the cached action graph like this?

Test Plan: Repeated `buck targets --show-output` is much faster locally.

Reviewed By: aiked

fbshipit-source-id: 6bcb826

Addepar/buck,rmaz/buck,Addepar/buck,ilya-klyuchnikov/buck,LegNeato/buck,dsyang/buck,LegNeato/buck,SeleniumHQ/buck,zpao/buck,ilya-klyuchnikov/buck,nguyentruongtho/buck,facebook/buck,Addepar/buck,clonetwin26/buck,robbertvanginkel/buck,zhan-xiong/buck,JoelMarcey/buck,robbertvanginkel/buck,kageiit/buck,shybovycha/buck,brettwooldridge/buck,clonetwin26/buck,clonetwin26/buck,Addepar/buck,rmaz/buck,zhan-xiong/buck,brettwooldridge/buck,k21/buck,marcinkwiatkowski/buck,dsyang/buck,Addepar/buck,JoelMarcey/buck,rmaz/buck,k21/buck,dsyang/buck,JoelMarcey/buck,SeleniumHQ/buck,zhan-xiong/buck,nguyentruongtho/buck,dsyang/buck,JoelMarcey/buck,rmaz/buck,ilya-klyuchnikov/buck,dsyang/buck,zhan-xiong/buck,romanoid/buck,kageiit/buck,zpao/buck,zhan-xiong/buck,LegNeato/buck,shybovycha/buck,brettwooldridge/buck,robbertvanginkel/buck,k21/buck,clonetwin26/buck,dsyang/buck,SeleniumHQ/buck,shs96c/buck,k21/buck,Addepar/buck,clonetwin26/buck,shs96c/buck,zhan-xiong/buck,nguyentruongtho/buck,JoelMarcey/buck,k21/buck,SeleniumHQ/buck,zpao/buck,facebook/buck,dsyang/buck,shybovycha/buck,shs96c/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,Addepar/buck,brettwooldridge/buck,k21/buck,shs96c/buck,LegNeato/buck,ilya-klyuchnikov/buck,SeleniumHQ/buck,marcinkwiatkowski/buck,clonetwin26/buck,SeleniumHQ/buck,kageiit/buck,k21/buck,romanoid/buck,romanoid/buck,zpao/buck,shybovycha/buck,JoelMarcey/buck,clonetwin26/buck,k21/buck,clonetwin26/buck,romanoid/buck,Addepar/buck,shybovycha/buck,robbertvanginkel/buck,clonetwin26/buck,JoelMarcey/buck,Addepar/buck,LegNeato/buck,dsyang/buck,zhan-xiong/buck,SeleniumHQ/buck,dsyang/buck,ilya-klyuchnikov/buck,kageiit/buck,shs96c/buck,romanoid/buck,shs96c/buck,romanoid/buck,LegNeato/buck,dsyang/buck,zhan-xiong/buck,kageiit/buck,clonetwin26/buck,clonetwin26/buck,JoelMarcey/buck,rmaz/buck,k21/buck,SeleniumHQ/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,shs96c/buck,shs96c/buck,marcinkwiatkowski/buck,brettwooldridge/buck,robbertvanginkel/buck,ilya-klyuchnikov/buck,SeleniumHQ/buck,brettwooldridge/buck,marcinkwiatkowski/buck,JoelMarcey/buck,shybovycha/buck,ilya-klyuchnikov/buck,facebook/buck,zhan-xiong/buck,robbertvanginkel/buck,brettwooldridge/buck,k21/buck,brettwooldridge/buck,LegNeato/buck,ilya-klyuchnikov/buck,shybovycha/buck,marcinkwiatkowski/buck,romanoid/buck,k21/buck,facebook/buck,shybovycha/buck,shybovycha/buck,brettwooldridge/buck,shybovycha/buck,robbertvanginkel/buck,rmaz/buck,LegNeato/buck,marcinkwiatkowski/buck,robbertvanginkel/buck,JoelMarcey/buck,k21/buck,marcinkwiatkowski/buck,zpao/buck,rmaz/buck,shybovycha/buck,ilya-klyuchnikov/buck,brettwooldridge/buck,romanoid/buck,marcinkwiatkowski/buck,brettwooldridge/buck,SeleniumHQ/buck,romanoid/buck,LegNeato/buck,nguyentruongtho/buck,SeleniumHQ/buck,clonetwin26/buck,robbertvanginkel/buck,LegNeato/buck,romanoid/buck,facebook/buck,shs96c/buck,romanoid/buck,dsyang/buck,SeleniumHQ/buck,SeleniumHQ/buck,LegNeato/buck,Addepar/buck,shybovycha/buck,marcinkwiatkowski/buck,romanoid/buck,brettwooldridge/buck,dsyang/buck,JoelMarcey/buck,rmaz/buck,Addepar/buck,rmaz/buck,LegNeato/buck,Addepar/buck,marcinkwiatkowski/buck,marcinkwiatkowski/buck,shs96c/buck,clonetwin26/buck,LegNeato/buck,facebook/buck,zhan-xiong/buck,rmaz/buck,zpao/buck,zhan-xiong/buck,zhan-xiong/buck,marcinkwiatkowski/buck,k21/buck,robbertvanginkel/buck,rmaz/buck,brettwooldridge/buck,nguyentruongtho/buck,zpao/buck,kageiit/buck,ilya-klyuchnikov/buck,ilya-klyuchnikov/buck,JoelMarcey/buck,robbertvanginkel/buck,rmaz/buck,romanoid/buck,Addepar/buck,JoelMarcey/buck,marcinkwiatkowski/buck,shs96c/buck,nguyentruongtho/buck,shybovycha/buck,rmaz/buck,nguyentruongtho/buck,shs96c/buck,dsyang/buck,kageiit/buck,shs96c/buck,facebook/buck,zhan-xiong/buck