Re: [libvirt] PATCH: Fix 2 build bugs on mingw

The Mingw platform lacks readlink(), so we stub out this method on that platform. The plain write() implementation of safezero() was not actually doing anything with the 'offset' arg. This makes it seek to the offset location before writing data. The mmap implementation of safezero() was also not quite right, truncating to len, so if offset was non-zero, it would not be large enough.