Looks like enable-shared defaults to false, so we actually
ended up with no usable object files in the lib output.
This also appears to have broken open-iscsi, as evinced by
/nix/store/[...]-binutils-2.27/bin/ld: cannot find -lisns
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:57: iscsid] Error 1
https://hydra.nixos.org/build/49437400/log/raw
With this patch, open-iscsi builds fine here.
