[test] Invert stdlib_dir conditional sense.
[test] Invert stdlib_dir conditional sense.

In #32903, a substitution pseudovariable was introduced to refer to the
path containing Swift.swiftmodule. Since builds on Linux put this file
in a path with a subdirectory named after the architecture name -- and
presumably builds on mac OS do not, a conditional was required to
distinguish these two cases.

However, builds on OpenBSD for example also put Swift.swiftmodule in a
similar subdirectory like Linux. Thus, invert the sense of this
conditional to encompass both Linux, OpenBSD, and make mac OS the
specific case, which it is here.

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