Allow building documentation out of the tree
Allow building documentation out of the tree

Patch originally provided by Gaudenz Steinlin <gaudenz@debian.org>

tklauser/libnl,dsahern/libnl,UnicronNL/libnl3,mshirley/libnl,cfriedt/libnl,UnicronNL/libnl3,vyos/libnl3,thom311/libnl,teto/libnl_old,HolyShitMan/libnl-1,tklauser/libnl,mshirley/libnl,HolyShitMan/libnl-1,karlhiramoto/libnl,tgraf/libnl,HolyShitMan/libnl-1,kolyshkin/libnl,kolyshkin/libnl,congwang/libnl,baloo/libnl,UnicronNL/libnl3,baloo/libnl,congwang/libnl,karlhiramoto/libnl,claudelee/libnl,vyos/libnl3,mshirley/libnl,congwang/libnl,chitranshi/libnl,claudelee/libnl,UnicronNL/libnl3,honsys/libnl,houstar/libnl,socketpair/libnl,tklauser/libnl,tklauser/libnl,socketpair/libnl,baloo/libnl,tgraf/libnl,houstar/libnl,kolyshkin/libnl,honsys/libnl,Distrotech/libnl,houstar/libnl,Distrotech/libnl,teto/libnl_old,greearb/libnl-ct,teto/libnl_old,baloo/libnl,chitranshi/libnl,thom311/libnl,houstar/libnl,chitranshi/libnl,cyclops8456/libnl3,chitranshi/libnl,dsahern/libnl,thom311/libnl,cyclops8456/libnl3,karlhiramoto/libnl,kolyshkin/libnl,teto/libnl_old,vyos/libnl3,dsahern/libnl,vyos/libnl3,cfriedt/libnl,cfriedt/libnl,mshirley/libnl,Distrotech/libnl,honsys/libnl,cyclops8456/libnl3,congwang/libnl,honsys/libnl,cyclops8456/libnl3,socketpair/libnl,cfriedt/libnl,greearb/libnl-ct,claudelee/libnl,Distrotech/libnl,karlhiramoto/libnl,claudelee/libnl,greearb/libnl-ct,tgraf/libnl,tgraf/libnl,dsahern/libnl,HolyShitMan/libnl-1