src: Fix macos build in process_singleton_posix.cc
src: Fix macos build in process_singleton_posix.cc

https://github.com/nwjs/chromium.src/commit/fdebe9cccc0d211f3d3cac582f18f49622cb42ff

nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,nwjs/nw.js,nwjs/nw.js