wpkg --output-repository-dir ...
The --output-repository-dir option is used along the --build command to specify where the resulting .deb files are expected to be saved. This option only works if the corresponding package defines a Distribution field with a valid path.
The final directory where the packages are saved is defined as:
<output-repository-dir>/<distribution-path>
Note that --output-repository-dir takes precedence over the --output-dir when both options are used together. The --output-dir option is still used for packages that do not define a Distribution path, though.