I ran into the same problem on julia 0.7. The workaround in that case was to
- build julia 0.7 on some other machine (with access to the internet)
- copy the
_build
directory to the non-networked machine, - run
touch doc/_build/html/en/index.html
. - run
make install
This tricked make install
into thinking the documentation was already up-to-date, so it doesn’t try to rebuild it, and therefore downloading packages.