By default, the OpenSC module is loaded as relative filename, i.e.
"opensc-pkcs11.so" is searched for in the default library path.
Point `LD_LIBRARY_PATH` for `digidoc-tool` to the OpenSC package just
like pkgs/tools/seurity/qdigidoc/deafult.nix already does.
This makes `digidoc-tool` work by default without manually setting
`LD_LIBRARY_PATH` or passing `--pkcs11=/path/to/module`.
Follow upstream once an appropiate patch has been merged.
e4dbad58d2