Update CI script to build against a common ancestor of origin/master and HEAD
Update CI script to build against a common ancestor of origin/master and HEAD

Also give advice for some changes to make to the script depending on the
environment and events triggering the script.

--
Change-Id: Ic230d96c29785c8df392b72fc4809eb7703fafff
Reviewed-on: https://bazel-review.googlesource.com/#/c/1570/
MOS_MIGRATED_REVID=97118314

manashmndl/bazel,ruo91/bazel,ButterflyNetwork/bazel,rhuss/bazel,ulfjack/bazel,d/bazel,kchodorow/bazel-1,katre/bazel,akira-baruah/bazel,kamalmarhubi/bazel,JackSullivan/bazel,mikelikespie/bazel,vt09/bazel,katre/bazel,hhclam/bazel,xindaya/bazel,asarazan/bazel,xindaya/bazel,Krasnyanskiy/bazel,kamalmarhubi/bazel,davidzchen/bazel,kchodorow/bazel,Ansahmadiba/bazel,meteorcloudy/bazel,werkt/bazel,nkhuyu/bazel,dropbox/bazel,rohitsaboo/bazel,kchodorow/bazel-1,akira-baruah/bazel,dslomov/bazel,rohitsaboo/bazel,joshua0pang/bazel,akira-baruah/bazel,bitemyapp/bazel,rhuss/bazel,kchodorow/bazel,d/bazel,Asana/bazel,meteorcloudy/bazel,juhalindfors/bazel-patches,LuminateWireless/bazel,LuminateWireless/bazel,bitemyapp/bazel,rhuss/bazel,dslomov/bazel,hhclam/bazel,juhalindfors/bazel-patches,perezd/bazel,ruo91/bazel,murugamsm/bazel,charlieaustin/bazel,damienmg/bazel,ulfjack/bazel,cushon/bazel,dhootha/bazel,charlieaustin/bazel,mrdomino/bazel,mikelikespie/bazel,xindaya/bazel,davidzchen/bazel,joshua0pang/bazel,joshua0pang/bazel,hermione521/bazel,sicipio/bazel,mbrukman/bazel,Ansahmadiba/bazel,Krasnyanskiy/bazel,meteorcloudy/bazel,dinowernli/bazel,kidaa/bazel,anupcshan/bazel,aehlig/bazel,twitter-forks/bazel,damienmg/bazel,ruo91/bazel,nkhuyu/bazel,kamalmarhubi/bazel,juhalindfors/bazel-patches,LuminateWireless/bazel,asarazan/bazel,hermione521/bazel,Ansahmadiba/bazel,meteorcloudy/bazel,rhuss/bazel,manashmndl/bazel,hhclam/bazel,kamalmarhubi/bazel,aehlig/bazel,twitter-forks/bazel,xindaya/bazel,snnn/bazel,JackSullivan/bazel,Krasnyanskiy/bazel,Topher-the-Geek/bazel,xindaya/bazel,spxtr/bazel,cushon/bazel,bitemyapp/bazel,aehlig/bazel,asarazan/bazel,twitter-forks/bazel,werkt/bazel,d/bazel,mbrukman/bazel,variac/bazel,dhootha/bazel,zhexuany/bazel,Digas29/bazel,JackSullivan/bazel,bitemyapp/bazel,sicipio/bazel,sicipio/bazel,davidzchen/bazel,mikelalcon/bazel,werkt/bazel,Topher-the-Geek/bazel,perezd/bazel,charlieaustin/bazel,vt09/bazel,Digas29/bazel,hermione521/bazel,murugamsm/bazel,perezd/bazel,dslomov/bazel,anupcshan/bazel,murugamsm/bazel,nkhuyu/bazel,murugamsm/bazel,Asana/bazel,murugamsm/bazel,anupcshan/bazel,akira-baruah/bazel,kchodorow/bazel-1,sicipio/bazel,Asana/bazel,meteorcloudy/bazel,mikelalcon/bazel,zhexuany/bazel,katre/bazel,ButterflyNetwork/bazel,rohitsaboo/bazel,dropbox/bazel,asarazan/bazel,Ansahmadiba/bazel,bitemyapp/bazel,safarmer/bazel,charlieaustin/bazel,charlieaustin/bazel,anupcshan/bazel,UrbanCompass/bazel,werkt/bazel,ruo91/bazel,dhootha/bazel,kchodorow/bazel,snnn/bazel,akira-baruah/bazel,Krasnyanskiy/bazel,spxtr/bazel,perezd/bazel,kchodorow/bazel-1,rohitsaboo/bazel,dinowernli/bazel,zhexuany/bazel,joshua0pang/bazel,ruo91/bazel,katre/bazel,mikelalcon/bazel,sicipio/bazel,dslomov/bazel,murugamsm/bazel,bitemyapp/bazel,Krasnyanskiy/bazel,gavares/bazel,Ansahmadiba/bazel,ulfjack/bazel,vt09/bazel,dropbox/bazel,snnn/bazel,Digas29/bazel,hhclam/bazel,dslomov/bazel-windows,vt09/bazel,dhootha/bazel,Topher-the-Geek/bazel,gavares/bazel,gavares/bazel,joshua0pang/bazel,gavares/bazel,kidaa/bazel,nkhuyu/bazel,dropbox/bazel,Krasnyanskiy/bazel,manashmndl/bazel,wakashige/bazel,Topher-the-Geek/bazel,ulfjack/bazel,ButterflyNetwork/bazel,ruo91/bazel,dslomov/bazel-windows,dslomov/bazel,kidaa/bazel,iamthearm/bazel,damienmg/bazel,asarazan/bazel,JackSullivan/bazel,ButterflyNetwork/bazel,Krasnyanskiy/bazel,dhootha/bazel,werkt/bazel,rohitsaboo/bazel,JackSullivan/bazel,bazelbuild/bazel,wakashige/bazel,dhootha/bazel,damienmg/bazel,aehlig/bazel,Digas29/bazel,kchodorow/bazel,LuminateWireless/bazel,meteorcloudy/bazel,safarmer/bazel,gavares/bazel,perezd/bazel,kamalmarhubi/bazel,rohitsaboo/bazel,ruo91/bazel,cushon/bazel,dslomov/bazel,davidzchen/bazel,snnn/bazel,cushon/bazel,whuwxl/bazel,mrdomino/bazel,variac/bazel,mrdomino/bazel,manashmndl/bazel,zhexuany/bazel,bitemyapp/bazel,cushon/bazel,Topher-the-Geek/bazel,zhexuany/bazel,gavares/bazel,meteorcloudy/bazel,mbrukman/bazel,kamalmarhubi/bazel,d/bazel,mikelikespie/bazel,iamthearm/bazel,mbrukman/bazel,dinowernli/bazel,spxtr/bazel,Digas29/bazel,whuwxl/bazel,manashmndl/bazel,gavares/bazel,snnn/bazel,abergmeier-dsfishlabs/bazel,UrbanCompass/bazel,bazelbuild/bazel,Ansahmadiba/bazel,UrbanCompass/bazel,kchodorow/bazel,mikelikespie/bazel,Asana/bazel,zhexuany/bazel,damienmg/bazel,UrbanCompass/bazel,bazelbuild/bazel,sicipio/bazel,twitter-forks/bazel,hhclam/bazel,dinowernli/bazel,dinowernli/bazel,spxtr/bazel,xindaya/bazel,mrdomino/bazel,mikelalcon/bazel,davidzchen/bazel,spxtr/bazel,dinowernli/bazel,werkt/bazel,kidaa/bazel,iamthearm/bazel,Topher-the-Geek/bazel,dropbox/bazel,perezd/bazel,juhalindfors/bazel-patches,kchodorow/bazel,variac/bazel,damienmg/bazel,d/bazel,nkhuyu/bazel,hermione521/bazel,mrdomino/bazel,vt09/bazel,joshua0pang/bazel,joshua0pang/bazel,katre/bazel,ulfjack/bazel,ulfjack/bazel,bazelbuild/bazel,twitter-forks/bazel,iamthearm/bazel,safarmer/bazel,Digas29/bazel,anupcshan/bazel,xindaya/bazel,snnn/bazel,iamthearm/bazel,nkhuyu/bazel,spxtr/bazel,aehlig/bazel,whuwxl/bazel,dslomov/bazel-windows,sicipio/bazel,UrbanCompass/bazel,wakashige/bazel,UrbanCompass/bazel,whuwxl/bazel,rhuss/bazel,variac/bazel,asarazan/bazel,aehlig/bazel,hermione521/bazel,bazelbuild/bazel,cushon/bazel,bazelbuild/bazel,nkhuyu/bazel,whuwxl/bazel,dslomov/bazel-windows,abergmeier-dsfishlabs/bazel,kchodorow/bazel-1,juhalindfors/bazel-patches,rhuss/bazel,juhalindfors/bazel-patches,safarmer/bazel,spxtr/bazel,gavares/bazel,manashmndl/bazel,kidaa/bazel,dhootha/bazel,Asana/bazel,twitter-forks/bazel,Ansahmadiba/bazel,twitter-forks/bazel,charlieaustin/bazel,hermione521/bazel,manashmndl/bazel,akira-baruah/bazel,LuminateWireless/bazel,murugamsm/bazel,wakashige/bazel,dslomov/bazel-windows,safarmer/bazel,ulfjack/bazel,mikelikespie/bazel,perezd/bazel,ButterflyNetwork/bazel,dropbox/bazel,dslomov/bazel-windows,juhalindfors/bazel-patches,katre/bazel,abergmeier-dsfishlabs/bazel,variac/bazel,Krasnyanskiy/bazel,mikelalcon/bazel,davidzchen/bazel,vt09/bazel,davidzchen/bazel,variac/bazel,hhclam/bazel,kchodorow/bazel-1,wakashige/bazel,Asana/bazel,snnn/bazel,whuwxl/bazel,mikelalcon/bazel,d/bazel,abergmeier-dsfishlabs/bazel,safarmer/bazel,JackSullivan/bazel,abergmeier-dsfishlabs/bazel,mbrukman/bazel,Topher-the-Geek/bazel,rhuss/bazel,aehlig/bazel,d/bazel,LuminateWireless/bazel,ButterflyNetwork/bazel,mrdomino/bazel,wakashige/bazel,charlieaustin/bazel,kchodorow/bazel,JackSullivan/bazel,asarazan/bazel,wakashige/bazel,abergmeier-dsfishlabs/bazel,Topher-the-Geek/bazel,mikelikespie/bazel,Asana/bazel,mbrukman/bazel,variac/bazel,kidaa/bazel,bitemyapp/bazel,anupcshan/bazel,damienmg/bazel,dslomov/bazel,iamthearm/bazel,kidaa/bazel,vt09/bazel,kidaa/bazel