schema-export does not work in plugins

**Problem**
If you create a plugin that defines domain objects using gorm hibernate5:6.1.12 calling `grails run-command schema-export` fails with `Command execution error: org.hibernate.tool.hbm2ddl.SchemaExport: method ()V not found`

If you create an app and try `grails schema-export`, it works as expected.
If you use the plugin in an application, `grails schema-export` also works as expected.

**Test project with readme:** https://github.com/pmcneil/testg3plugin

**Use case for schema-export in a plugin:** existing grails 2 plugin https://github.com/bio-org-au/nsl-domain-plugin uses schema-export to build an executable schema to set up new shard databases and create upgrade scripts.

Start with the linked test project and its README, then reproduce the failure with `grails run-command schema-export` in a plugin defining domain objects with gorm hibernate5:6.1.12. Compare this with schema export in an application and in an application using the plugin; done means plugin-defined domain objects can be exported without the SchemaExport constructor error.

Written by the indexing model from the issue text.