[WIP] Add build script and rebuild deps with it and -fPIC

Ref neovim/neovim#905. Build made with new script: https://travis-ci.org/neovim/neovim/builds/29826692.

Note `patch -p1 << EOF` lines: it would actually be better if there was a way to specify them as cmake options, but currently this does not work.

Waiting for travis to complete to mark it as `RDY`.