There are many little technical details in the whole process of setting up and
using an HSM with opensc, this one seems to have a pretty simple answer:
providing a symlink common path to opensc-pkcs11.so on all arches.  I propose
adding a symlink to e.g. /usr/lib/x86_64-linux-gnu/opensc-pkcs11.so that is
/usr/lib/opensc-pkcs11.so, so config files can use the same path on all arches.

I've been working to smooth out a lot of little details like this in the whole
process, you can see the documentation of my efforts here:

https://guardianproject.info/2014/03/28/security-in-a-thumb-drive-the-promise-and-pain-of-hardware-security-modules-take-one/

https://dev.guardianproject.info/projects/bazaar/wiki/Improving_the_APK_Signing_Procedure

I thought I'd add a bit more explanation.  For things like Java to use opensc,
people have to use a conf file.  that conf file has to include the path to
opensc-pkcs11.so.  Having that path the same on all archs makes things a lot
simpler.  Other things also need to reference that .so, like:

  pkcs11-tool --module /usr/lib/opensc-pkcs11.so --list-slots

I haven't found an 'official' way of doing this yet...

The opensc-pkcs11 package is marked as Multi-Arch: same, so this won't happen.
I have looked around in Debian to find an example of any pkcs11 module and they are all set up
without such a symbolic link.