Clear output folder before generating artefact
Clear output folder before generating artefact

This is to avoid including files left from previous builds

gds-attic/transactions-explorer,alphagov/transactions-explorer,gds-attic/transactions-explorer,gds-attic/transactions-explorer,gds-attic/transactions-explorer,gds-attic/transactions-explorer,alphagov/transactions-explorer,alphagov/transactions-explorer,alphagov/transactions-explorer,alphagov/transactions-explorer