Buck: Clarify how to delete the build cache
Buck: Clarify how to delete the build cache

Inspired-By: David Ostrovsky <aa743a0aaec8f7d7a1f01442503957f4d7a2d634@ostrovsky.org>
Change-Id: I1e98d9bcf63c289a52ab4643d2cc047622209e5a

qtproject/qtqa-gerrit,netroby/gerrit,Distrotech/gerrit,thinkernel/gerrit,quyixia/gerrit,MerritCR/merrit,WANdisco/gerrit,anminhsu/gerrit,TonyChai24/test,anminhsu/gerrit,Seinlin/gerrit,quyixia/gerrit,Overruler/gerrit,thesamet/gerrit,pkdevbox/gerrit,GerritCodeReview/gerrit,renchaorevee/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,MerritCR/merrit,supriyantomaftuh/gerrit,Distrotech/gerrit,Seinlin/gerrit,jackminicloud/test,thinkernel/gerrit,GerritCodeReview/gerrit,pkdevbox/gerrit,anminhsu/gerrit,thesamet/gerrit,quyixia/gerrit,netroby/gerrit,renchaorevee/gerrit,netroby/gerrit,Distrotech/gerrit,thesamet/gerrit,MerritCR/merrit,TonyChai24/test,jackminicloud/test,dwhipstock/gerrit,gcoders/gerrit,supriyantomaftuh/gerrit,thinkernel/gerrit,Seinlin/gerrit,GerritCodeReview/gerrit,pkdevbox/gerrit,WANdisco/gerrit,Overruler/gerrit,hdost/gerrit,netroby/gerrit,WANdisco/gerrit,Overruler/gerrit,hdost/gerrit,hdost/gerrit,Seinlin/gerrit,MerritCR/merrit,thinkernel/gerrit,jackminicloud/test,jackminicloud/test,quyixia/gerrit,supriyantomaftuh/gerrit,MerritCR/merrit,anminhsu/gerrit,Seinlin/gerrit,pkdevbox/gerrit,jackminicloud/test,netroby/gerrit,netroby/gerrit,renchaorevee/gerrit,joshuawilson/merrit,TonyChai24/test,joshuawilson/merrit,MerritCR/merrit,Seinlin/gerrit,MerritCR/merrit,gerrit-review/gerrit,Distrotech/gerrit,gerrit-review/gerrit,quyixia/gerrit,dwhipstock/gerrit,qtproject/qtqa-gerrit,thesamet/gerrit,TonyChai24/test,supriyantomaftuh/gerrit,dwhipstock/gerrit,gcoders/gerrit,gcoders/gerrit,GerritCodeReview/gerrit,Seinlin/gerrit,joshuawilson/merrit,anminhsu/gerrit,thinkernel/gerrit,joshuawilson/merrit,supriyantomaftuh/gerrit,renchaorevee/gerrit,jackminicloud/test,gerrit-review/gerrit,thinkernel/gerrit,anminhsu/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,Distrotech/gerrit,gerrit-review/gerrit,hdost/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,quyixia/gerrit,dwhipstock/gerrit,dwhipstock/gerrit,joshuawilson/merrit,supriyantomaftuh/gerrit,renchaorevee/gerrit,jackminicloud/test,gerrit-review/gerrit,TonyChai24/test,thinkernel/gerrit,TonyChai24/test,dwhipstock/gerrit,gcoders/gerrit,renchaorevee/gerrit,hdost/gerrit,Distrotech/gerrit,pkdevbox/gerrit,GerritCodeReview/gerrit,joshuawilson/merrit,joshuawilson/merrit,dwhipstock/gerrit,MerritCR/merrit,Overruler/gerrit,gcoders/gerrit,qtproject/qtqa-gerrit,thesamet/gerrit,GerritCodeReview/gerrit,pkdevbox/gerrit,WANdisco/gerrit,thesamet/gerrit,quyixia/gerrit,hdost/gerrit,hdost/gerrit,netroby/gerrit,WANdisco/gerrit,Overruler/gerrit,joshuawilson/merrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,TonyChai24/test,Overruler/gerrit,gcoders/gerrit,supriyantomaftuh/gerrit,gerrit-review/gerrit,anminhsu/gerrit,gcoders/gerrit,thesamet/gerrit,renchaorevee/gerrit,pkdevbox/gerrit,Distrotech/gerrit