Set a new attribute to the builder with an arbitrary value.
If an attribute with attr_type already exists in the builder then it is changed to the new value, otherwise an attribute is
added.
The memory in value is copied by the builder.
null may be specified for the value argument, in which case an empty attribute is created. [constINVALID
] may be specified for the length, in which case an invalid attribute is created in the PKCS#11 style.
| this |
the builder |
| attr_type |
the attribute type |
| value |
the new attribute memory |
| length |
the length of the memory |