Fix Win32 detection on latest Rakudo.
Fix Win32 detection on latest Rakudo.

timo/panda,sjn/panda,raydiak/panda,hoelzro/panda,masak/panda,will-crawford/panda,tadzik/panda,raydiak/panda,stmuk/panda,jonathanstowe/panda,skaji/panda,TimToady/panda,masak/panda,niner/panda,shoichikaji/panda,perlpilot/panda,laben/panda,stmuk/panda,cygx/panda,moznion/panda,hoelzro/panda,will-crawford/panda,dwarring/panda,jonathanstowe/panda,skaji/panda,dwarring/panda,timo/panda,tadzik/panda,moznion/panda,sjn/panda,shoichikaji/panda,dwarring/panda,TimToady/panda,sjn/panda,laben/panda,hoelzro/panda,perlpilot/panda,nbrown/panda,niner/panda,tadzik/panda,cygx/panda,nbrown/panda