/usr/bin/ld manpage and help should indicate '-soname' not '--soname'
$/usr/bin/ld -z help ... [-h name], [--soname name] use 'name' as internal shared object identifier ... $ man /usr/bin/ld ... -h name --soname name In dynamic mode only, when building a shared object, records name in the object's dynamic section. name is recorded in any dynamic objects that are linked with this object rather than the object's file system name. Accordingly, name is used by the runtime linker as the name of the shared object to search for at runtime. See Recording a Shared Object Name in Linker and Libraries Guide.
sun ld has never supported '--soname', only '-soname' as do gnu ld and gold. These strings should be fixed.