consider affinity when computing active cpus on Linux#199

MadCoder merged 1 commit intoswiftlang:masterswiftlang/swift-corelibs-libdispatch:masterfrom

dgrove-oss:hwconfig-respect-affinitydgrove-oss/swift-corelibs-libdispatch:hwconfig-respect-affinityCopy head branch name to clipboard