Update capp to use CAPP_BUILD if present, falling back to STEAM_BUILD, erroring if neither.
Update capp to use CAPP_BUILD if present, falling back to STEAM_BUILD, erroring if neither.

akshell/cappuccino,eventualbuddha/cappuccino,FrankReh/cappuccino,cappuccino/cappuccino,AlexanderMazaletskiy/cappuccino,tancred/cappuccino,cappuccino/cappuccino,cacaodev/cappuccino,Rosch/cappuccino,dgvivero/CappCoreData,deltaprojects/cappuccino,zittix/cappuccino,zittix/cappuccino,akshell/cappuccino,AlexanderMazaletskiy/cappuccino,280north/cappuccino,Rosch/cappuccino,AlexanderMazaletskiy/cappuccino,enquora/cappuccino,krodelin/cappuccino,enquora/cappuccino,mrcarlberg/cappuccino,primalmotion/cappuccino,rgv151/cappuccino,zittix/cappuccino,primalmotion/cappuccino,primalmotion/cappuccino,cacaodev/cappuccino,cacaodev/cappuccino,krodelin/cappuccino,kidaa/cappuccino,tolmasky/cappuccino,deltaprojects/cappuccino,deltaprojects/cappuccino,deltaprojects/cappuccino,rgv151/cappuccino,mrcarlberg/cappuccino,cacaodev/cappuccino,jarib/cappuccino,tancred/cappuccino,koamac/Cappuccino,tancred/cappuccino,dgvivero/CappCoreData,280north/cappuccino,cappuccino/cappuccino,rgv151/cappuccino,enquora/cappuccino,tancred/cappuccino,eventualbuddha/cappuccino,krodelin/cappuccino,koamac/Cappuccino,daboe01/cappuccino,Dogild/cappuccino,AlexanderMazaletskiy/cappuccino,eventualbuddha/cappuccino,koamac/Cappuccino,tolmasky/cappuccino,tancred/cappuccino,FrankReh/cappuccino,FrankReh/cappuccino,kidaa/cappuccino,zittix/cappuccino,tolmasky/cappuccino,mrcarlberg/cappuccino,FrankReh/cappuccino,rgv151/cappuccino,Dogild/cappuccino,wangshijin/cappuccino,cacaodev/cappuccino,kidaa/cappuccino,FrankReh/cappuccino,enquora/cappuccino,FrankReh/cappuccino,Rosch/cappuccino,mrcarlberg/cappuccino,enquora/cappuccino,deltaprojects/cappuccino,tolmasky/cappuccino,jiangshen/cappuccino,krodelin/cappuccino,enquora/cappuccino,wangshijin/cappuccino,Rosch/cappuccino,Dogild/cappuccino,kidaa/cappuccino,AlexanderMazaletskiy/cappuccino,akshell/cappuccino,cacaodev/cappuccino,zittix/cappuccino,Rosch/cappuccino,krodelin/cappuccino,mrcarlberg/cappuccino,daboe01/cappuccino,mrcarlberg/cappuccino,primalmotion/cappuccino,enquora/cappuccino,koamac/Cappuccino,FrankReh/cappuccino,280north/cappuccino,akshell/cappuccino,koamac/Cappuccino,primalmotion/cappuccino,rgv151/cappuccino,jarib/cappuccino,tancred/cappuccino,AlexanderMazaletskiy/cappuccino,Dogild/cappuccino,mrcarlberg/cappuccino,cacaodev/cappuccino,wangshijin/cappuccino,daboe01/cappuccino,deltaprojects/cappuccino,cappuccino/cappuccino,Dogild/cappuccino,daboe01/cappuccino,zittix/cappuccino,dgvivero/CappCoreData,FrankReh/cappuccino,primalmotion/cappuccino,280north/cappuccino,Rosch/cappuccino,280north/cappuccino,krodelin/cappuccino,zittix/cappuccino,kidaa/cappuccino,krodelin/cappuccino,Dogild/cappuccino,cappuccino/cappuccino,dgvivero/CappCoreData,Dogild/cappuccino,daboe01/cappuccino,cappuccino/cappuccino,daboe01/cappuccino,rgv151/cappuccino,wangshijin/cappuccino,dgvivero/CappCoreData,mrcarlberg/cappuccino,cappuccino/cappuccino,tolmasky/cappuccino,eventualbuddha/cappuccino,primalmotion/cappuccino,wangshijin/cappuccino,wangshijin/cappuccino,daboe01/cappuccino,jiangshen/cappuccino,kidaa/cappuccino,Rosch/cappuccino,deltaprojects/cappuccino,koamac/Cappuccino,rgv151/cappuccino