arc package: add option to specify config file
arc package: add option to specify config file

Summary: We'd like to specify a config file for deployments -- add an option for that.

Test Plan:
Built an RPM with a custom config file containing values for `root_restrict_files`, and installed it locally. Saw that the config file was installed in `/etc/watchman.json`. Created an empty
directory called `foo` and ran `watchman watch $PWD/foo`. Saw that watchman refused to watch it, claiming that none of the files in `root_restrict_files` were present.

Reviewers: wez

Reviewed By: wez

Differential Revision: https://phabricator.fb.com/D902566

Task ID: 2647765

--HG--
extra : rebase_source : 10f332fa3d8cf124e43a9f4b48f80a37a8dff6a0
extra : amend_source : dbf038d98c981e0d5d08bedffc49399164f34cde

dcolascione/laptop-watchman,windofthesky/watchman,yun63/watchman,sdgdsffdsfff/watchman,windofthesky/watchman,kevinsawicki/watchman,twitter/watchman,Ziriax/watchman,facebook/watchman,twitter/watchman,michalliu/watchman,yonglehou/watchman,michalliu/watchman,supriyantomaftuh/watchman,montogeek/watchman,webmasteraxe/watchman,webmasteraxe/watchman,masoncloud/watchman,amasad/watchman,supriyantomaftuh/watchman,kwlzn/watchman,yangeagle/watchman,besarthoxhaj/watchman,michalliu/watchman,facebook/watchman,sdgdsffdsfff/watchman,Jonekee/watchman,wez/watchman,kwlzn/watchman,twitter/watchman,montogeek/watchman,masoncloud/watchman,wez/watchman,nodakai/watchman,nodakai/watchman,Ziriax/watchman,yonglehou/watchman,hanhailong/watchman,masoncloud/watchman,Ziriax/watchman,twitter/watchman,windofthesky/watchman,supriyantomaftuh/watchman,bhamiltoncx/watchman,dhruvsinghal/watchman,dhruvsinghal/watchman,yun63/watchman,webmasteraxe/watchman,yun63/watchman,exponentjs/watchman,wez/watchman,amasad/watchman,michalliu/watchman,hanhailong/watchman,nodakai/watchman,hanhailong/watchman,facebook/watchman,yun63/watchman,webmasteraxe/watchman,bitemyapp/watchman,montogeek/watchman,bhamiltoncx/watchman,amasad/watchman,exponentjs/watchman,bitemyapp/watchman,nodakai/watchman,bitemyapp/watchman,sdgdsffdsfff/watchman,Jonekee/watchman,sdgdsffdsfff/watchman,bhamiltoncx/watchman,dhruvsinghal/watchman,amasad/watchman,yangeagle/watchman,yonglehou/watchman,montogeek/watchman,masoncloud/watchman,michalliu/watchman,windofthesky/watchman,besarthoxhaj/watchman,facebook/watchman,yonglehou/watchman,twitter/watchman,wez/watchman,dcolascione/laptop-watchman,nodakai/watchman,alanwill/watchman,phmx/watchman,phmx/watchman,Jonekee/watchman,windofthesky/watchman,sdgdsffdsfff/watchman,phmx/watchman,sdgdsffdsfff/watchman,facebook/watchman,nodakai/watchman,wez/watchman,nodakai/watchman,Jonekee/watchman,michalliu/watchman,kevinsawicki/watchman,phmx/watchman,kevinsawicki/watchman,Ziriax/watchman,supriyantomaftuh/watchman,masoncloud/watchman,dhruvsinghal/watchman,montogeek/watchman,masoncloud/watchman,facebook/watchman,yun63/watchman,hanhailong/watchman,facebook/watchman,yonglehou/watchman,yonglehou/watchman,sdgdsffdsfff/watchman,yangeagle/watchman,kwlzn/watchman,windofthesky/watchman,supriyantomaftuh/watchman,kevinsawicki/watchman,yun63/watchman,Jonekee/watchman,kwlzn/watchman,masoncloud/watchman,kwlzn/watchman,besarthoxhaj/watchman,besarthoxhaj/watchman,dcolascione/laptop-watchman,kevinsawicki/watchman,bhamiltoncx/watchman,dhruvsinghal/watchman,bitemyapp/watchman,bhamiltoncx/watchman,hanhailong/watchman,michalliu/watchman,nodakai/watchman,amasad/watchman,sdgdsffdsfff/watchman,exponentjs/watchman,webmasteraxe/watchman,alanwill/watchman,hanhailong/watchman,dcolascione/laptop-watchman,yun63/watchman,bitemyapp/watchman,dhruvsinghal/watchman,dcolascione/laptop-watchman,wez/watchman,facebook/watchman,exponentjs/watchman,twitter/watchman,yangeagle/watchman,dcolascione/laptop-watchman,besarthoxhaj/watchman,twitter/watchman,windofthesky/watchman,bitemyapp/watchman,phmx/watchman,montogeek/watchman,amasad/watchman,yun63/watchman,wez/watchman,supriyantomaftuh/watchman,wez/watchman,alanwill/watchman,phmx/watchman,webmasteraxe/watchman,kwlzn/watchman,bhamiltoncx/watchman,supriyantomaftuh/watchman,kevinsawicki/watchman,amasad/watchman,twitter/watchman,Jonekee/watchman,dcolascione/laptop-watchman,webmasteraxe/watchman,exponentjs/watchman,montogeek/watchman,bitemyapp/watchman,dhruvsinghal/watchman,yangeagle/watchman,webmasteraxe/watchman,Ziriax/watchman,alanwill/watchman,yangeagle/watchman,hanhailong/watchman,besarthoxhaj/watchman,nodakai/watchman,amasad/watchman,dhruvsinghal/watchman,alanwill/watchman,facebook/watchman,Jonekee/watchman,supriyantomaftuh/watchman,yonglehou/watchman,alanwill/watchman,kevinsawicki/watchman,yonglehou/watchman,wez/watchman,besarthoxhaj/watchman,yangeagle/watchman,dcolascione/laptop-watchman,masoncloud/watchman,hanhailong/watchman,Ziriax/watchman,Jonekee/watchman,besarthoxhaj/watchman,montogeek/watchman,kwlzn/watchman,exponentjs/watchman,michalliu/watchman,bitemyapp/watchman