Build/install gflags' static library on build hosts.
Build/install gflags' static library on build hosts.

As of [homebrew #41151](https://github.com/Homebrew/homebrew/pull/41151) gflags is not installed with a static library.
Our build hosts must have static versions of gflags.

eastebry/osquery,mchugh19/osquery,unixboy/osquery,glensc/osquery,blackfist/osquery,mgoffin/osquery,alex/osquery,tinixx/osquery,silentspirit0005/osquery,gnawhleinad/osquery,mwielgoszewski/osquery,prabhakhar/osquery,blackfist/osquery,jacknagz/osquery,mofarrell/osquery,grayark/osquery,unixboy/osquery,chitrang/osquery,jacques-n/osquery,glensc/osquery,anusornc/osquery,isghe/osquery,mofarrell/osquery,jajce/osquery,hackgnar/osquery,mgoffin/osquery,jedi22/osquery,arirubinstein/osquery,siddhartharay007/osquery,anusornc/osquery,trizt/osquery,jacques-n/osquery,justintime32/osquery,silentspirit0005/osquery,venkateshdaram434/osquery,kk9599/osquery,kk9599/osquery,achmiel/osquery,Abhikos/osquery,jacknagz/osquery,digideskio/osquery,prabhakhar/osquery,mwielgoszewski/osquery,jedi22/osquery,eastebry/osquery,linearregression/osquery,Abhikos/osquery,runt18/osquery,anusornc/osquery,glensc/osquery,jajce/osquery,PickmanSec/osquery,arirubinstein/osquery,kost/osquery,takumikub/osquery,alonashu/osquery,gnawhleinad/osquery,jajce/osquery,jacques-n/osquery,digideskio/osquery,alex/osquery,0xdabbad00/osquery,kost/osquery,alonashu/osquery,alonashu/osquery,SEC-squad/osquery,gnawhleinad/osquery,pathcl/osquery,venkateshdaram434/osquery,daukantas/osquery,linearregression/osquery,pathcl/osquery,takumikub/osquery,runasand/osquery,palashahuja/osquery,dushmis/osquery,cesarmarinhorj/osquery,trizt/osquery,SEC-squad/osquery,tburgin/osquery,honestme/osquery,tinixx/osquery,achmiel/osquery,mgoffin/osquery,tburgin/osquery,chitrang/osquery,arirubinstein/osquery,PoppySeedPlehzr/osquery,linearregression/osquery,tburgin/osquery,mlw/osquery,isghe/osquery,venkateshdaram434/osquery,isghe/osquery,unixboy/osquery,hackgnar/osquery,honestme/osquery,friedbutter/osquery,cesarmarinhorj/osquery,kk9599/osquery,runasand/osquery,achmiel/osquery,mlw/osquery,dushmis/osquery,honestme/osquery,digideskio/osquery,daukantas/osquery,PickmanSec/osquery,runt18/osquery,mchugh19/osquery,adream307/osquery,jedi22/osquery,palashahuja/osquery,pathcl/osquery,SEC-squad/osquery,PoppySeedPlehzr/osquery,runasand/osquery,eastebry/osquery,tinixx/osquery,justintime32/osquery,hackgnar/osquery,kost/osquery,mlw/osquery,grayark/osquery,siddhartharay007/osquery,justintime32/osquery,chitrang/osquery,Abhikos/osquery,PickmanSec/osquery,mchugh19/osquery,mofarrell/osquery,runt18/osquery,PoppySeedPlehzr/osquery,friedbutter/osquery,palashahuja/osquery,takumikub/osquery,alex/osquery,friedbutter/osquery,jacknagz/osquery,trizt/osquery,cesarmarinhorj/osquery,adream307/osquery,blackfist/osquery,silentspirit0005/osquery,siddhartharay007/osquery,dushmis/osquery,prabhakhar/osquery,daukantas/osquery,grayark/osquery,adream307/osquery,0xdabbad00/osquery,0xdabbad00/osquery,mwielgoszewski/osquery