Point the lib/calamares/libcalamares.so symlink to the versioned so.

Point the lib/calamares/libcalamares.so symlink for the Python modules
directly to the versioned lib/libcalamares.so.VERSION library rather
than to the lib/libcalamares.so symlink. This allows distributions to
install the lib/libcalamares.so symlink to a development package and
only ship lib/libcalamares.so.VERSION and lib/calamares/libcalamares.so
in the runtime package. It is also marginally faster (because only one
level of symlinks has to be resolved instead of two).

(I know this works because I have been manually fixing up this symlink
in the Fedora specfile so far.)