Timely close directory stream.
Timely close directory stream.

Summary:
This wasn't being closed explicitly, let's do that so directory handles don't
hang around.

Test Plan:
On mac, do:

  buck build ...
  lsof -p <BUCKDPID>
  buck build ...
  lsof -p <BUCKDPID>

See that no directory file handles are open for apple sdk directories.

Reviewed By: Coneko

fbshipit-source-id: e5982cc

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