build: fix a typo resulting in an invalid variable
build: fix a typo resulting in an invalid variable

Correct the definition of SWIFT_HOST_VARIANT_ARCH_default which was
followed by a comma resulting in the variable name having a trailing
comma.  Correct the variable name.

xwu/swift,airspeedswift/swift,natecook1000/swift,tkremenek/swift,tkremenek/swift,sschiau/swift,parkera/swift,lorentey/swift,sschiau/swift,rudkx/swift,stephentyrone/swift,stephentyrone/swift,huonw/swift,devincoughlin/swift,stephentyrone/swift,gregomni/swift,tkremenek/swift,gribozavr/swift,alblue/swift,jmgc/swift,nathawes/swift,practicalswift/swift,xedin/swift,jmgc/swift,austinzheng/swift,amraboelela/swift,practicalswift/swift,austinzheng/swift,harlanhaskins/swift,alblue/swift,brentdax/swift,jckarter/swift,karwa/swift,jckarter/swift,shahmishal/swift,parkera/swift,airspeedswift/swift,shajrawi/swift,jckarter/swift,huonw/swift,CodaFi/swift,jopamer/swift,shajrawi/swift,rudkx/swift,rudkx/swift,lorentey/swift,danielmartin/swift,karwa/swift,shajrawi/swift,brentdax/swift,shahmishal/swift,aschwaighofer/swift,airspeedswift/swift,gregomni/swift,jopamer/swift,shajrawi/swift,apple/swift,austinzheng/swift,CodaFi/swift,CodaFi/swift,stephentyrone/swift,hooman/swift,shajrawi/swift,harlanhaskins/swift,CodaFi/swift,tkremenek/swift,parkera/swift,danielmartin/swift,parkera/swift,shahmishal/swift,lorentey/swift,gribozavr/swift,gribozavr/swift,sschiau/swift,alblue/swift,jckarter/swift,devincoughlin/swift,allevato/swift,JGiola/swift,allevato/swift,allevato/swift,devincoughlin/swift,brentdax/swift,jopamer/swift,xwu/swift,shajrawi/swift,danielmartin/swift,gribozavr/swift,natecook1000/swift,nathawes/swift,glessard/swift,brentdax/swift,gregomni/swift,jopamer/swift,austinzheng/swift,tkremenek/swift,ahoppen/swift,brentdax/swift,gregomni/swift,harlanhaskins/swift,nathawes/swift,sschiau/swift,benlangmuir/swift,apple/swift,austinzheng/swift,harlanhaskins/swift,devincoughlin/swift,danielmartin/swift,shahmishal/swift,benlangmuir/swift,roambotics/swift,atrick/swift,danielmartin/swift,devincoughlin/swift,devincoughlin/swift,aschwaighofer/swift,lorentey/swift,alblue/swift,atrick/swift,huonw/swift,jmgc/swift,practicalswift/swift,parkera/swift,jopamer/swift,roambotics/swift,glessard/swift,JGiola/swift,gribozavr/swift,ahoppen/swift,shajrawi/swift,alblue/swift,jopamer/swift,ahoppen/swift,natecook1000/swift,parkera/swift,gribozavr/swift,roambotics/swift,gregomni/swift,karwa/swift,atrick/swift,amraboelela/swift,karwa/swift,hooman/swift,shahmishal/swift,natecook1000/swift,devincoughlin/swift,amraboelela/swift,hooman/swift,glessard/swift,JGiola/swift,roambotics/swift,jmgc/swift,apple/swift,glessard/swift,hooman/swift,alblue/swift,shahmishal/swift,xedin/swift,xwu/swift,huonw/swift,karwa/swift,harlanhaskins/swift,xwu/swift,xedin/swift,practicalswift/swift,shajrawi/swift,practicalswift/swift,airspeedswift/swift,ahoppen/swift,shahmishal/swift,jckarter/swift,natecook1000/swift,CodaFi/swift,austinzheng/swift,JGiola/swift,huonw/swift,apple/swift,xedin/swift,ahoppen/swift,xwu/swift,karwa/swift,roambotics/swift,karwa/swift,xedin/swift,ahoppen/swift,allevato/swift,nathawes/swift,aschwaighofer/swift,austinzheng/swift,nathawes/swift,amraboelela/swift,xwu/swift,xedin/swift,jckarter/swift,natecook1000/swift,allevato/swift,sschiau/swift,lorentey/swift,practicalswift/swift,huonw/swift,amraboelela/swift,brentdax/swift,natecook1000/swift,jmgc/swift,stephentyrone/swift,xedin/swift,stephentyrone/swift,CodaFi/swift,jckarter/swift,gregomni/swift,hooman/swift,atrick/swift,CodaFi/swift,lorentey/swift,allevato/swift,JGiola/swift,aschwaighofer/swift,airspeedswift/swift,benlangmuir/swift,roambotics/swift,gribozavr/swift,rudkx/swift,jmgc/swift,hooman/swift,practicalswift/swift,JGiola/swift,allevato/swift,atrick/swift,apple/swift,benlangmuir/swift,danielmartin/swift,apple/swift,xwu/swift,amraboelela/swift,parkera/swift,practicalswift/swift,sschiau/swift,aschwaighofer/swift,parkera/swift,lorentey/swift,tkremenek/swift,karwa/swift,brentdax/swift,tkremenek/swift,benlangmuir/swift,aschwaighofer/swift,amraboelela/swift,rudkx/swift,alblue/swift,airspeedswift/swift,glessard/swift,glessard/swift,airspeedswift/swift,atrick/swift,rudkx/swift,hooman/swift,gribozavr/swift,devincoughlin/swift,stephentyrone/swift,jmgc/swift,jopamer/swift,lorentey/swift,danielmartin/swift,nathawes/swift,nathawes/swift,sschiau/swift,harlanhaskins/swift,aschwaighofer/swift,huonw/swift,xedin/swift,sschiau/swift,benlangmuir/swift,shahmishal/swift,harlanhaskins/swift