test: simplify Windows configuration, categorise (NFC)
test: simplify Windows configuration, categorise (NFC)

Simplify the Windows MSVC runtime library flag calculation.  Categorise
the Darwin, android, Windows options.

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