[windows] Compare SWIFT_HOST_VARIANT against lowercase value.
[windows] Compare SWIFT_HOST_VARIANT against lowercase value.

SWIFT_HOST_VARIANT is lowercase. SWIFT_HOST_VARIANT_SDK is uppercase.

Compare against the right one.

This tries to fix #29805, which didn't fix the CI for Windows VS2017.

benlangmuir/swift,atrick/swift,jmgc/swift,allevato/swift,tkremenek/swift,roambotics/swift,xwu/swift,parkera/swift,aschwaighofer/swift,allevato/swift,nathawes/swift,harlanhaskins/swift,benlangmuir/swift,tkremenek/swift,jmgc/swift,glessard/swift,ahoppen/swift,aschwaighofer/swift,hooman/swift,stephentyrone/swift,jmgc/swift,tkremenek/swift,harlanhaskins/swift,allevato/swift,stephentyrone/swift,aschwaighofer/swift,rudkx/swift,parkera/swift,xwu/swift,roambotics/swift,parkera/swift,atrick/swift,jckarter/swift,harlanhaskins/swift,hooman/swift,benlangmuir/swift,xwu/swift,xwu/swift,allevato/swift,nathawes/swift,parkera/swift,atrick/swift,parkera/swift,CodaFi/swift,aschwaighofer/swift,airspeedswift/swift,allevato/swift,JGiola/swift,hooman/swift,gregomni/swift,xwu/swift,CodaFi/swift,tkremenek/swift,ahoppen/swift,glessard/swift,jckarter/swift,JGiola/swift,roambotics/swift,jmgc/swift,hooman/swift,rudkx/swift,gregomni/swift,JGiola/swift,ahoppen/swift,nathawes/swift,JGiola/swift,harlanhaskins/swift,xwu/swift,airspeedswift/swift,stephentyrone/swift,hooman/swift,atrick/swift,JGiola/swift,apple/swift,airspeedswift/swift,roambotics/swift,ahoppen/swift,benlangmuir/swift,apple/swift,apple/swift,aschwaighofer/swift,jmgc/swift,JGiola/swift,airspeedswift/swift,jckarter/swift,harlanhaskins/swift,atrick/swift,airspeedswift/swift,allevato/swift,hooman/swift,stephentyrone/swift,gregomni/swift,parkera/swift,roambotics/swift,airspeedswift/swift,CodaFi/swift,rudkx/swift,glessard/swift,benlangmuir/swift,CodaFi/swift,gregomni/swift,ahoppen/swift,parkera/swift,xwu/swift,benlangmuir/swift,CodaFi/swift,tkremenek/swift,gregomni/swift,CodaFi/swift,apple/swift,glessard/swift,apple/swift,jckarter/swift,tkremenek/swift,rudkx/swift,jmgc/swift,airspeedswift/swift,glessard/swift,nathawes/swift,ahoppen/swift,roambotics/swift,gregomni/swift,tkremenek/swift,aschwaighofer/swift,nathawes/swift,stephentyrone/swift,stephentyrone/swift,nathawes/swift,jckarter/swift,jmgc/swift,nathawes/swift,allevato/swift,stephentyrone/swift,rudkx/swift,jckarter/swift,hooman/swift,atrick/swift,aschwaighofer/swift,parkera/swift,CodaFi/swift,rudkx/swift,harlanhaskins/swift,jckarter/swift,apple/swift,glessard/swift,harlanhaskins/swift