Makefiles: do not use variables if they are undefined
Makefiles: do not use variables if they are undefined

wkennington/rethinkdb,matthaywardwebdesign/rethinkdb,wkennington/rethinkdb,marshall007/rethinkdb,sebadiaz/rethinkdb,marshall007/rethinkdb,urandu/rethinkdb,scripni/rethinkdb,urandu/rethinkdb,RubenKelevra/rethinkdb,bpradipt/rethinkdb,jmptrader/rethinkdb,dparnell/rethinkdb,wojons/rethinkdb,gdi2290/rethinkdb,Qinusty/rethinkdb,RubenKelevra/rethinkdb,JackieXie168/rethinkdb,losywee/rethinkdb,AntouanK/rethinkdb,wojons/rethinkdb,yaolinz/rethinkdb,sontek/rethinkdb,matthaywardwebdesign/rethinkdb,grandquista/rethinkdb,sontek/rethinkdb,sontek/rethinkdb,niieani/rethinkdb,mquandalle/rethinkdb,captainpete/rethinkdb,robertjpayne/rethinkdb,victorbriz/rethinkdb,sbusso/rethinkdb,wkennington/rethinkdb,alash3al/rethinkdb,rrampage/rethinkdb,losywee/rethinkdb,rrampage/rethinkdb,AntouanK/rethinkdb,niieani/rethinkdb,JackieXie168/rethinkdb,rrampage/rethinkdb,greyhwndz/rethinkdb,bpradipt/rethinkdb,rrampage/rethinkdb,wujf/rethinkdb,JackieXie168/rethinkdb,grandquista/rethinkdb,dparnell/rethinkdb,4talesa/rethinkdb,Qinusty/rethinkdb,lenstr/rethinkdb,captainpete/rethinkdb,ayumilong/rethinkdb,yaolinz/rethinkdb,mbroadst/rethinkdb,sebadiaz/rethinkdb,gavioto/rethinkdb,spblightadv/rethinkdb,AntouanK/rethinkdb,dparnell/rethinkdb,JackieXie168/rethinkdb,jmptrader/rethinkdb,bchavez/rethinkdb,catroot/rethinkdb,victorbriz/rethinkdb,eliangidoni/rethinkdb,yakovenkodenis/rethinkdb,4talesa/rethinkdb,greyhwndz/rethinkdb,4talesa/rethinkdb,sbusso/rethinkdb,lenstr/rethinkdb,robertjpayne/rethinkdb,RubenKelevra/rethinkdb,alash3al/rethinkdb,Qinusty/rethinkdb,sebadiaz/rethinkdb,niieani/rethinkdb,spblightadv/rethinkdb,yakovenkodenis/rethinkdb,gavioto/rethinkdb,losywee/rethinkdb,robertjpayne/rethinkdb,sontek/rethinkdb,jesseditson/rethinkdb,alash3al/rethinkdb,captainpete/rethinkdb,grandquista/rethinkdb,matthaywardwebdesign/rethinkdb,ayumilong/rethinkdb,losywee/rethinkdb,ayumilong/rethinkdb,ajose01/rethinkdb,robertjpayne/rethinkdb,alash3al/rethinkdb,KSanthanam/rethinkdb,Qinusty/rethinkdb,tempbottle/rethinkdb,niieani/rethinkdb,grandquista/rethinkdb,scripni/rethinkdb,rrampage/rethinkdb,sbusso/rethinkdb,captainpete/rethinkdb,Wilbeibi/rethinkdb,losywee/rethinkdb,yaolinz/rethinkdb,losywee/rethinkdb,elkingtonmcb/rethinkdb,scripni/rethinkdb,captainpete/rethinkdb,matthaywardwebdesign/rethinkdb,robertjpayne/rethinkdb,matthaywardwebdesign/rethinkdb,victorbriz/rethinkdb,lenstr/rethinkdb,gavioto/rethinkdb,wkennington/rethinkdb,robertjpayne/rethinkdb,lenstr/rethinkdb,bchavez/rethinkdb,urandu/rethinkdb,rrampage/rethinkdb,sontek/rethinkdb,victorbriz/rethinkdb,mbroadst/rethinkdb,4talesa/rethinkdb,wojons/rethinkdb,Qinusty/rethinkdb,JackieXie168/rethinkdb,lenstr/rethinkdb,bpradipt/rethinkdb,greyhwndz/rethinkdb,KSanthanam/rethinkdb,mcanthony/rethinkdb,eliangidoni/rethinkdb,alash3al/rethinkdb,mcanthony/rethinkdb,jesseditson/rethinkdb,matthaywardwebdesign/rethinkdb,Qinusty/rethinkdb,gavioto/rethinkdb,gdi2290/rethinkdb,elkingtonmcb/rethinkdb,Wilbeibi/rethinkdb,yaolinz/rethinkdb,Qinusty/rethinkdb,wujf/rethinkdb,sebadiaz/rethinkdb,dparnell/rethinkdb,lenstr/rethinkdb,grandquista/rethinkdb,bchavez/rethinkdb,ajose01/rethinkdb,eliangidoni/rethinkdb,bchavez/rethinkdb,mquandalle/rethinkdb,ajose01/rethinkdb,wkennington/rethinkdb,catroot/rethinkdb,bchavez/rethinkdb,catroot/rethinkdb,jmptrader/rethinkdb,robertjpayne/rethinkdb,bpradipt/rethinkdb,losywee/rethinkdb,jmptrader/rethinkdb,urandu/rethinkdb,gavioto/rethinkdb,mbroadst/rethinkdb,sbusso/rethinkdb,scripni/rethinkdb,ayumilong/rethinkdb,Qinusty/rethinkdb,grandquista/rethinkdb,catroot/rethinkdb,gavioto/rethinkdb,elkingtonmcb/rethinkdb,wujf/rethinkdb,robertjpayne/rethinkdb,wojons/rethinkdb,ayumilong/rethinkdb,elkingtonmcb/rethinkdb,pap/rethinkdb,ayumilong/rethinkdb,AntouanK/rethinkdb,urandu/rethinkdb,captainpete/rethinkdb,captainpete/rethinkdb,ajose01/rethinkdb,wujf/rethinkdb,scripni/rethinkdb,jesseditson/rethinkdb,marshall007/rethinkdb,grandquista/rethinkdb,KSanthanam/rethinkdb,greyhwndz/rethinkdb,pap/rethinkdb,bchavez/rethinkdb,alash3al/rethinkdb,yakovenkodenis/rethinkdb,jmptrader/rethinkdb,Wilbeibi/rethinkdb,sontek/rethinkdb,losywee/rethinkdb,ajose01/rethinkdb,KSanthanam/rethinkdb,bpradipt/rethinkdb,tempbottle/rethinkdb,rrampage/rethinkdb,KSanthanam/rethinkdb,mbroadst/rethinkdb,bpradipt/rethinkdb,lenstr/rethinkdb,wojons/rethinkdb,mquandalle/rethinkdb,catroot/rethinkdb,greyhwndz/rethinkdb,wkennington/rethinkdb,rrampage/rethinkdb,niieani/rethinkdb,spblightadv/rethinkdb,4talesa/rethinkdb,wujf/rethinkdb,sbusso/rethinkdb,victorbriz/rethinkdb,4talesa/rethinkdb,victorbriz/rethinkdb,sbusso/rethinkdb,sbusso/rethinkdb,sebadiaz/rethinkdb,elkingtonmcb/rethinkdb,dparnell/rethinkdb,ayumilong/rethinkdb,Wilbeibi/rethinkdb,mcanthony/rethinkdb,wojons/rethinkdb,gavioto/rethinkdb,greyhwndz/rethinkdb,niieani/rethinkdb,jesseditson/rethinkdb,ajose01/rethinkdb,urandu/rethinkdb,urandu/rethinkdb,wojons/rethinkdb,matthaywardwebdesign/rethinkdb,mquandalle/rethinkdb,catroot/rethinkdb,spblightadv/rethinkdb,jmptrader/rethinkdb,marshall007/rethinkdb,mquandalle/rethinkdb,Antoua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