This reverts commit 763f5d787316ec1b041450a644ecd9416f11e94f.
Currently the vfork() code path in opkg is broken and relies on unsupported
ftello() / fseeko() operations on pipes - we need to restructure the code
before we can reconsider this approach.
Signed-off-by: Jo-Philipp Wich <jo@mein.io>