Bootstrap.mak: Add macosx alias for osx to match Premake os.host()
Bootstrap.mak: Add macosx alias for osx to match Premake os.host()

dcourtois/premake-core,noresources/premake-core,starkos/premake-core,premake/premake-core,sleepingwit/premake-core,premake/premake-core,mandersan/premake-core,noresources/premake-core,dcourtois/premake-core,mandersan/premake-core,dcourtois/premake-core,dcourtois/premake-core,starkos/premake-core,sleepingwit/premake-core,mandersan/premake-core,mandersan/premake-core,premake/premake-core,noresources/premake-core,sleepingwit/premake-core,starkos/premake-core,LORgames/premake-core,noresources/premake-core,premake/premake-core,dcourtois/premake-core,noresources/premake-core,noresources/premake-core,premake/premake-core,starkos/premake-core,LORgames/premake-core,premake/premake-core,starkos/premake-core,noresources/premake-core,premake/premake-core,sleepingwit/premake-core,LORgames/premake-core,starkos/premake-core,dcourtois/premake-core,LORgames/premake-core,dcourtois/premake-core,starkos/premake-core,mandersan/premake-core,LORgames/premake-core,sleepingwit/premake-core