build: use some variables for the defaults
build: use some variables for the defaults

Use variables for the defaults to normalise the paths through the
various hosts.  This makes a follow up refactoring more obvious.

lorentey/swift,shajrawi/swift,apple/swift,danielmartin/swift,airspeedswift/swift,devincoughlin/swift,JGiola/swift,tkremenek/swift,nathawes/swift,karwa/swift,allevato/swift,nathawes/swift,shajrawi/swift,karwa/swift,alblue/swift,sschiau/swift,amraboelela/swift,stephentyrone/swift,ahoppen/swift,gregomni/swift,ahoppen/swift,aschwaighofer/swift,parkera/swift,danielmartin/swift,hooman/swift,gribozavr/swift,lorentey/swift,gregomni/swift,gregomni/swift,jckarter/swift,alblue/swift,parkera/swift,shajrawi/swift,brentdax/swift,jckarter/swift,rudkx/swift,xedin/swift,stephentyrone/swift,devincoughlin/swift,xwu/swift,tkremenek/swift,danielmartin/swift,gregomni/swift,sschiau/swift,allevato/swift,harlanhaskins/swift,brentdax/swift,CodaFi/swift,benlangmuir/swift,lorentey/swift,airspeedswift/swift,xedin/swift,rudkx/swift,benlangmuir/swift,karwa/swift,gribozavr/swift,stephentyrone/swift,hooman/swift,tkremenek/swift,amraboelela/swift,karwa/swift,brentdax/swift,nathawes/swift,austinzheng/swift,practicalswift/swift,lorentey/swift,tkremenek/swift,lorentey/swift,airspeedswift/swift,practicalswift/swift,jmgc/swift,CodaFi/swift,atrick/swift,airspeedswift/swift,shahmishal/swift,aschwaighofer/swift,harlanhaskins/swift,glessard/swift,jckarter/swift,CodaFi/swift,harlanhaskins/swift,devincoughlin/swift,apple/swift,airspeedswift/swift,amraboelela/swift,roambotics/swift,practicalswift/swift,sschiau/swift,benlangmuir/swift,devincoughlin/swift,atrick/swift,apple/swift,alblue/swift,shajrawi/swift,shajrawi/swift,austinzheng/swift,stephentyrone/swift,glessard/swift,lorentey/swift,austinzheng/swift,practicalswift/swift,glessard/swift,austinzheng/swift,gribozavr/swift,alblue/swift,jmgc/swift,atrick/swift,glessard/swift,nathawes/swift,danielmartin/swift,nathawes/swift,austinzheng/swift,danielmartin/swift,aschwaighofer/swift,jmgc/swift,allevato/swift,jckarter/swift,JGiola/swift,benlangmuir/swift,rudkx/swift,glessard/swift,xwu/swift,parkera/swift,sschiau/swift,hooman/swift,apple/swift,parkera/swift,gribozavr/swift,hooman/swift,rudkx/swift,alblue/swift,aschwaighofer/swift,alblue/swift,CodaFi/swift,ahoppen/swift,sschiau/swift,gregomni/swift,devincoughlin/swift,stephentyrone/swift,JGiola/swift,karwa/swift,allevato/swift,jckarter/swift,atrick/swift,practicalswift/swift,ahoppen/swift,lorentey/swift,nathawes/swift,atrick/swift,CodaFi/swift,sschiau/swift,nathawes/swift,harlanhaskins/swift,parkera/swift,gribozavr/swift,xedin/swift,karwa/swift,austinzheng/swift,CodaFi/swift,practicalswift/swift,roambotics/swift,devincoughlin/swift,benlangmuir/swift,danielmartin/swift,xedin/swift,apple/swift,JGiola/swift,xedin/swift,gribozavr/swift,CodaFi/swift,austinzheng/swift,jmgc/swift,stephentyrone/swift,amraboelela/swift,hooman/swift,rudkx/swift,brentdax/swift,JGiola/swift,ahoppen/swift,gregomni/swift,apple/swift,hooman/swift,parkera/swift,roambotics/swift,shajrawi/swift,jmgc/swift,shahmishal/swift,xedin/swift,amraboelela/swift,alblue/swift,shahmishal/swift,roambotics/swift,parkera/swift,brentdax/swift,gribozavr/swift,karwa/swift,sschiau/swift,parkera/swift,amraboelela/swift,allevato/swift,rudkx/swift,shahmishal/swift,tkremenek/swift,atrick/swift,harlanhaskins/swift,xwu/swift,stephentyrone/swift,hooman/swift,shajrawi/swift,airspeedswift/swift,aschwaighofer/swift,gribozavr/swift,aschwaighofer/swift,JGiola/swift,devincoughlin/swift,xedin/swift,benlangmuir/swift,allevato/swift,lorentey/swift,shahmishal/swift,airspeedswift/swift,jmgc/swift,devincoughlin/swift,shahmishal/swift,danielmartin/swift,xedin/swift,xwu/swift,roambotics/swift,karwa/swift,amraboelela/swift,shajrawi/swift,jmgc/swift,roambotics/swift,brentdax/swift,harlanhaskins/swift,brentdax/swift,xwu/swift,harlanhaskins/swift,shahmishal/swift,ahoppen/swift,aschwaighofer/swift,shahmishal/swift,tkremenek/swift,allevato/swift,xwu/swift,tkremenek/swift,practicalswift/swift,glessard/swift,practicalswift/swift,jckarter/swift,xwu/swift,jckarter/swift,sschiau/swift