Update to latest zig and include paths.h

The latest version of libuv requires the paths.h header from libc. Updated the tool to work with the latest development version of zig, and included paths.h into headers.c. I unfortunately only have the sysroot available for MacOS 13 and seem to have issues downloading/mounting the other sysroot versions. cc @kubkon if you could also run and push paths.h for the older sysroot versions via. `fetch-them-macos-headers fetch`. Resolves #24.