Fail the configure script if you don't have boost
Fail the configure script if you don't have boost

Summary:
Discovered this while trying to build folly on OS X. It would print a
warning about Boost being missing that got drowned out in the rest of
the configure output, and then the build would fail. This makes the
failure more friendly.

Test Plan:
`autoreconf; ./configure` on a system without boost
installed; make sure configure fails and the last thing it prints is the
boost error message.

Reviewed By: delong.j@fb.com

FB internal diff: D797389

kernelim/folly,lifei/folly,gavioto/folly,gavioto/folly,Hincoin/folly,yangjin-unique/folly,zhiweicai/folly,raphaelamorim/folly,PPC64/folly,CJstar/folly,raphaelamorim/folly,constantine001/folly,xzmagic/folly,doctaweeks/folly,facebook/folly,Orvid/folly,guker/folly,xzmagic/folly,SeanRBurton/folly,colemancda/folly,upsoft/folly,stonegithubs/folly,kernelim/folly,ykarlsbrun/folly,Hincoin/folly,reddit/folly,guker/folly,ykarlsbrun/folly,sonnyhu/folly,stonegithubs/folly,loversInJapan/folly,romange/folly,unmeshvrije/C--,cppfool/folly,alexst07/folly,tomhughes/folly,clearlinux/folly,theiver9827/folly,wildinto/folly,PoisonBOx/folly,stonegithubs/folly,Orvid/folly,cole14/folly,bikong2/folly,floxard/folly,upsoft/folly,loverszhaokai/folly,lifei/folly,xzmagic/folly,sonnyhu/folly,sonnyhu/folly,sakishum/folly,sakishum/folly,yangjin-unique/folly,cole14/folly,doctaweeks/folly,renyinew/folly,kernelim/folly,mqeizi/folly,fw1121/folly,PPC64/folly,SammyK/folly,CJstar/folly,Hincoin/folly,SeanRBurton/folly,leolujuyi/folly,xzmagic/folly,brunomorishita/folly,loverszhaokai/folly,rklabs/folly,alexst07/folly,bikong2/folly,arg0/folly,loversInJapan/folly,zhiweicai/folly,clearlinux/folly,rklabs/folly,theiver9827/folly,zhiweicai/folly,ykarlsbrun/folly,SammyK/folly,unmeshvrije/C--,mqeizi/folly,cppfool/folly,wildinto/folly,zhiweicai/folly,PoisonBOx/folly,hongliangzhao/folly,shaobz/folly,reddit/folly,upsoft/folly,unmeshvrije/C--,arg0/folly,bsampath/folly,bobegir/folly,fw1121/folly,facebook/folly,charsyam/folly,nickhen/folly,bsampath/folly,project-zerus/folly,renyinew/folly,KSreeHarsha/folly,clearlinux/folly,bobegir/folly,SeanRBurton/folly,gaoyingie/folly,brunomorishita/folly,alexst07/folly,chjp2046/folly,loversInJapan/folly,lifei/folly,leolujuyi/folly,raphaelamorim/folly,clearlylin/folly,cppfool/folly,project-zerus/folly,clearlinux/folly,floxard/folly,SammyK/folly,cppfool/folly,sakishum/folly,bsampath/folly,brunomorishita/folly,leolujuyi/folly,rklabs/folly,SeanRBurton/folly,guker/folly,juniway/folly,gaoyingie/folly,PPC64/folly,KSreeHarsha/folly,mqeizi/folly,Eagle-X/folly,romange/folly,sakishum/folly,project-zerus/folly,renyinew/folly,nickhen/folly,ykarlsbrun/folly,tempbottle/folly,PoisonBOx/folly,theiver9827/folly,sakishum/folly,bowlofstew/folly,doctaweeks/folly,wildinto/folly,ykarlsbrun/folly,loverszhaokai/folly,romange/folly,CJstar/folly,bobegir/folly,cole14/folly,colemancda/folly,leolujuyi/folly,fw1121/folly,wildinto/folly,gaoyingie/folly,leolujuyi/folly,yangjin-unique/folly,tomhughes/folly,mqeizi/folly,tomhughes/folly,rklabs/folly,mqeizi/folly,Eagle-X/folly,theiver9827/folly,brunomorishita/folly,bikong2/folly,renyinew/folly,juniway/folly,stonegithubs/folly,Hincoin/folly,gavioto/folly,zhiweicai/folly,tempbottle/folly,Eagle-X/folly,facebook/folly,Eagle-X/folly,PoisonBOx/folly,reddit/folly,PPC64/folly,charsyam/folly,tomhughes/folly,chjp2046/folly,sonnyhu/folly,constantine001/folly,CJstar/folly,yangjin-unique/folly,floxard/folly,wildinto/folly,unmeshvrije/C--,hongliangzhao/folly,KSreeHarsha/folly,nickhen/folly,clearlylin/folly,bowlofstew/folly,constantine001/folly,SammyK/folly,bikong2/folly,arg0/folly,kernelim/folly,fw1121/folly,juniway/folly,colemancda/folly,tempbottle/folly,cole14/folly,SammyK/folly,juniway/folly,kernelim/folly,hongliangzhao/folly,alexst07/folly,chjp2046/folly,constantine001/folly,bowlofstew/folly,cole14/folly,lifei/folly,hongliangzhao/folly,brunomorishita/folly,sonnyhu/folly,Orvid/folly,bsampath/folly,theiver9827/folly,SeanRBurton/folly,bowlofstew/folly,loverszhaokai/folly,charsyam/folly,clearlylin/folly,hongliangzhao/folly,tomhughes/folly,chjp2046/folly,KSreeHarsha/folly,CJstar/folly,unmeshvrije/C--,rklabs/folly,gavioto/folly,doctaweeks/folly,fw1121/folly,romange/folly,yangjin-unique/folly,facebook/folly,arg0/folly,bobegir/folly,PPC64/folly,floxard/folly,nickhen/folly,tempbottle/folly,gaoyingie/folly,gavioto/folly,guker/folly,reddit/folly,constantine001/folly,Eagle-X/folly,loversInJapan/folly,raphaelamorim/folly,floxard/folly,KSreeHarsha/folly,shaobz/folly,clearlylin/folly,project-zerus/folly,shaobz/folly,bowlofstew/folly,raphaelamorim/folly,cppfool/folly,colemancda/folly,facebook/folly,charsyam/folly,upsoft/folly,juniway/folly,clearlinux/folly,bsampath/folly,lifei/folly,PoisonBOx/folly,clearlylin/folly,Orvid/folly,colemancda/folly,project-zerus/folly,bikong2/folly,loverszhaokai/folly,upsoft/folly,loversInJapan/folly,Orvid/folly,guker/folly,shaobz/folly,romange/folly,shaobz/folly,alexst07/folly,arg0/folly,tempbottle/folly,Hincoin/folly,doctaweeks/folly,unmeshvrije/C--,reddit/folly,xzmagic/folly,renyinew/folly,gaoyingie/folly,stonegithubs/folly,chjp2046/folly,bobegir/folly,nickhen/folly