build: fix build on cygwin
build: fix build on cygwin

Cygwin has getifaddrs(), but not AF_LINK, leading to:

util/virstats.c: In function 'virNetInterfaceStats':
util/virstats.c:138:41: error: 'AF_LINK' undeclared (first use in this function)
         if (ifa->ifa_addr->sa_family != AF_LINK)
...

* src/util/virstats.c (virNetInterfaceStats): Only use getifaddrs
if AF_LINK is present.

Signed-off-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

elmarco/libvirt,andreabolognani/libvirt,datto/libvirt,elmarco/libvirt,taget/libvirt,taget/libvirt,rlaager/libvirt,crobinso/libvirt,jardasgit/libvirt,nertpinx/libvirt,jardasgit/libvirt,shugaoye/libvirt,zippy2/libvirt,crobinso/libvirt,eskultety/libvirt,agx/libvirt,eskultety/libvirt,eskultety/libvirt,shugaoye/libvirt,datto/libvirt,jfehlig/libvirt,eskultety/libvirt,libvirt/libvirt,VenkatDatta/libvirt,datto/libvirt,jardasgit/libvirt,shugaoye/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,eskultety/libvirt,rlaager/libvirt,libvirt/libvirt,olafhering/libvirt,taget/libvirt,jfehlig/libvirt,crobinso/libvirt,nertpinx/libvirt,agx/libvirt,VenkatDatta/libvirt,olafhering/libvirt,libvirt/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,taget/libvirt,agx/libvirt,shugaoye/libvirt,andreabolognani/libvirt,olafhering/libvirt,elmarco/libvirt,andreabolognani/libvirt,jardasgit/libvirt,rlaager/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,nertpinx/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,elmarco/libvirt,VenkatDatta/libvirt,rlaager/libvirt,zippy2/libvirt,datto/libvirt,crobinso/libvirt,shugaoye/libvirt,datto/libvirt,fabianfreyer/libvirt,agx/libvirt,taget/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,elmarco/libvirt,nertpinx/libvirt,andreabolognani/libvirt,olafhering/libvirt,rlaager/libvirt,zippy2/libvirt,agx/libvirt,zippy2/libvirt,libvirt/libvirt