Fix some Linux inconsistencies with swift_*weak runtime functions
Fix some Linux inconsistencies with swift_*weak runtime functions

Some of these return void * on platforms with Objective-C interop,
but drops the return value on those without, such as on Linux.

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