Runtime: restrict behaviour to cygwin
Runtime: restrict behaviour to cygwin

__int128 is not available as an extension on MSVC nor clang for Windows.
Restrict the behaviour to cygwin only.

ben-ng/swift,russbishop/swift,rudkx/swift,rudkx/swift,milseman/swift,shahmishal/swift,OscarSwanros/swift,gottesmm/swift,kstaring/swift,stephentyrone/swift,karwa/swift,hooman/swift,alblue/swift,tkremenek/swift,danielmartin/swift,CodaFi/swift,calebd/swift,devincoughlin/swift,frootloops/swift,xedin/swift,djwbrown/swift,uasys/swift,modocache/swift,modocache/swift,allevato/swift,allevato/swift,therealbnut/swift,jckarter/swift,shajrawi/swift,CodaFi/swift,austinzheng/swift,harlanhaskins/swift,lorentey/swift,apple/swift,roambotics/swift,felix91gr/swift,OscarSwanros/swift,xedin/swift,gribozavr/swift,swiftix/swift,jtbandes/swift,arvedviehweger/swift,deyton/swift,djwbrown/swift,jopamer/swift,benlangmuir/swift,tardieu/swift,hooman/swift,airspeedswift/swift,manavgabhawala/swift,sschiau/swift,bitjammer/swift,karwa/swift,tjw/swift,jckarter/swift,aschwaighofer/swift,ahoppen/swift,jtbandes/swift,arvedviehweger/swift,swiftix/swift,tardieu/swift,arvedviehweger/swift,jopamer/swift,atrick/swift,shajrawi/swift,hughbe/swift,hooman/swift,benlangmuir/swift,uasys/swift,gregomni/swift,brentdax/swift,alblue/swift,codestergit/swift,return/swift,manavgabhawala/swift,tardieu/swift,jmgc/swift,huonw/swift,xwu/swift,parkera/swift,natecook1000/swift,jtbandes/swift,hughbe/swift,JGiola/swift,swiftix/swift,danielmartin/swift,stephentyrone/swift,atrick/swift,kstaring/swift,return/swift,russbishop/swift,nathawes/swift,practicalswift/swift,calebd/swift,harlanhaskins/swift,shahmishal/swift,harlanhaskins/swift,Jnosh/swift,kperryua/swift,manavgabhawala/swift,amraboelela/swift,sschiau/swift,lorentey/swift,JaSpa/swift,lorentey/swift,glessard/swift,JGiola/swift,harlanhaskins/swift,huonw/swift,jtbandes/swift,aschwaighofer/swift,gmilos/swift,milseman/swift,shahmishal/swift,gottesmm/swift,zisko/swift,practicalswift/swift,CodaFi/swift,practicalswift/swift,tardieu/swift,arvedviehweger/swift,ahoppen/swift,IngmarStein/swift,gribozavr/swift,gottesmm/swift,bitjammer/swift,zisko/swift,milseman/swift,practicalswift/swift,tkremenek/swift,tjw/swift,austinzheng/swift,arvedviehweger/swift,JGiola/swift,djwbrown/swift,natecook1000/swift,atrick/swift,shahmishal/swift,tjw/swift,modocache/swift,codestergit/swift,tjw/swift,atrick/swift,tkremenek/swift,Jnosh/swift,natecook1000/swift,jckarter/swift,zisko/swift,frootloops/swift,manavgabhawala/swift,return/swift,zisko/swift,gribozavr/swift,deyton/swift,return/swift,hooman/swift,jmgc/swift,JaSpa/swift,deyton/swift,devincoughlin/swift,tkremenek/swift,gregomni/swift,JaSpa/swift,gregomni/swift,benlangmuir/swift,IngmarStein/swift,apple/swift,danielmartin/swift,nathawes/swift,benlangmuir/swift,apple/swift,tardieu/swift,allevato/swift,gribozavr/swift,shajrawi/swift,russbishop/swift,djwbrown/swift,kstaring/swift,milseman/swift,amraboelela/swift,benlangmuir/swift,natecook1000/swift,gribozavr/swift,gregomni/swift,gregomni/swift,shahmishal/swift,frootloops/swift,tinysun212/swift-windows,milseman/swift,shajrawi/swift,karwa/swift,gmilos/swift,danielmartin/swift,sschiau/swift,huonw/swift,jmgc/swift,brentdax/swift,devincoughlin/swift,alblue/swift,alblue/swift,tkremenek/swift,arvedviehweger/swift,airspeedswift/swift,jtbandes/swift,austinzheng/swift,austinzheng/swift,russbishop/swift,uasys/swift,airspeedswift/swift,ahoppen/swift,calebd/swift,djwbrown/swift,parkera/swift,parkera/swift,huonw/swift,frootloops/swift,jckarter/swift,ben-ng/swift,bitjammer/swift,amraboelela/swift,parkera/swift,xwu/swift,brentdax/swift,allevato/swift,stephentyrone/swift,therealbnut/swift,amraboelela/swift,modocache/swift,aschwaighofer/swift,return/swift,glessard/swift,apple/swift,karwa/swift,harlanhaskins/swift,tkremenek/swift,sschiau/swift,gottesmm/swift,therealbnut/swift,ben-ng/swift,deyton/swift,xwu/swift,kstaring/swift,airspeedswift/swift,swiftix/swift,roambotics/swift,calebd/swift,OscarSwanros/swift,practicalswift/swift,kperryua/swift,jopamer/swift,practicalswift/swift,CodaFi/swift,allevato/swift,calebd/swift,jopamer/swift,felix91gr/swift,gottesmm/swift,roambotics/swift,rudkx/swift,tinysun212/swift-windows,jtbandes/swift,atrick/swift,brentdax/swift,aschwaighofer/swift,danielmartin/swift,frootloops/swift,xwu/swift,tjw/swift,parkera/swift,xedin/swift,alblue/swift,huonw/swift,return/swift,zisko/swift,lorentey/swift,brentdax/swift,jopamer/swift,tardieu/swift,Jnosh/swift,glessard/swift,ben-ng/swift,karwa/swift,brentdax/swift,hooman/swift,CodaFi/swift,xedin/swift,tkremenek/swift,tjw/swift,glessard/swift,lorentey/swift,shahmishal/swift,felix91gr/swift,jmgc/swift,manavgabhawala/swift,apple/swift,Jnosh/swift,lorentey/swift,kperryua/swift,alblue/swift,manavgabhawala/swift,ahoppen/swift,nathawes/swift,nathawes/swift,felix91gr/swift,frootloops/swift,hughbe/swift,danielmartin/swift,shajrawi/swift,kperryua/swift,shajrawi/swift,roambotics/swift,felix91gr/swift,deyton/swift,alblue/swift,tinysun212/swift-windows,brentdax/swift,glessard/swift,jopamer/swift,devincoughlin/swift,IngmarStein/swift,gmilos/swift,allevato/swift,gottesmm/swift,lorentey/swift,CodaFi/swift,austinzheng/swift,gmilos/swift,devincoughlin/swift,gmilos/swift,return/swift,xwu/swift,gribozavr/swift,swiftix/swift,shahmishal/swift,deyton/swift,uasys/swift,therealbnut/swift,parkera/swift,frootloops/swift,bitjammer/swift,djwbrown/swift,hooman/swift,nathawes/swift,IngmarStein/swift,gribozavr/swift,manavgabhawala/swift,calebd/swift,jmgc/swift,ben-ng/swift,aschwaighofer/swift,tinysun212/swift-windows,hooman/swift,jckarter/swift,djwbrown/swift,stephentyrone/swift,shajrawi/swift,natecook1000/swift,milseman/swift,JGiola/swift,allevato/swift,russbishop/swift,modocache/swift,parkera/swift,kperryua/swift,therealbnut/swift,devincoughlin/swift,jmgc/swift,OscarSwanros/swift,bitjammer/swift,xwu/swift,JGiola/swift,benlangmuir/swift,tinysun212/swift-windows,glessard/swift,stephentyrone/swift,CodaFi/swift,sschiau/swift,jtbandes/swift,tinysun212/swift-windows,kperryua/swift,aschwaighofer/swift,russbishop/swift,Jnosh/swift,amraboelela/swift,stephentyrone/swift,swiftix/swift,devincoughlin/swift,practicalswift/swift,codestergit/swift,codestergit/swift,JaSpa/swift,OscarSwanros/swift,natecook1000/swift,codestergit/swift,Jnosh/swift,JaSpa/swift,OscarSwanros/swift,amraboelela/swift,airspeedswift/swift,atrick/swift,gmilos/swift,JGiola/swift,apple/swift,JaSpa/swift,tjw/swift,huonw/swift,harlanhaskins/swift,parkera/swift,lorentey/swift,sschiau/swift,austinzheng/swift,russbishop/swift,codestergit/swift,sschiau/swift,jmgc/swift,ben-ng/swift,jopamer/swift,kperryua/swift,kstaring/swift,felix91gr/swift,ahoppen/swift,kstaring/swift,roambotics/swift,codestergit/swift,bitjammer/swift,xwu/swift,IngmarStein/swift,modocache/swift,xedin/swift,jckarter/swift,felix91gr/swift,karwa/swift,natecook1000/swift,IngmarStein/swift,deyton/swift,austinzheng/swift,jckarter/swift,xedin/swift,gregomni/swift,gmilos/swift,nathawes/swift,rudkx/swift,hughbe/swift,calebd/swift,rudkx/swift,xedin/swift,modocache/swift,Jnosh/swift,hughbe/swift,tardieu/swift,devincoughlin/swift,practicalswift/swift,bitjammer/swift,stephentyrone/swift,aschwaighofer/swift,hughbe/swift,huonw/swift,ahoppen/swift,uasys/swift,zisko/swift,kstaring/swift,uasys/swift,danielmartin/swift,roambotics/swift,shajrawi/swift,karwa/swift,zisko/swift,IngmarStein/swift,xedin/swift,amraboelela/swift,sschiau/swift,uasys/swift,therealbnut/swift,JaSpa/swift,ben-ng/swift,gottesmm/swift,therealbnut/swift,tinysun212/swift-windows,airspeedswift/swift,hughbe/swift,arvedviehweger/swift,harlanhaskins/swift,rudkx/swift,milseman/swift,gribozavr/swift,shahmishal/swift,swiftix/swift,karwa/swift,nathawes/swift,OscarSwanros/swift,airspeedswift/swift