jupyter lab build ignores .yarnrc settings (v1.0.0rc0)

[pkvprakash]

Installing a labextension or building jupyterlab assets tend to ignore the .yarnrc settings.
I have overridden the default registry in my .yarnrc settings with an Nexus npm package proxy. But the latest jupyterlab (1.0.0rc0) build tend to ignore those settings and tries to pull the changes from registry.yarnpkg.com directly.

[blink1073]

cf #4149

[RedTn]

@blink1073

This hasn't been fixed or has it? I'm following the related material but it's not clear to me how to change the registry if it's fixed.
I'm trying a .yarnrc file of
registry "https://www.myregistry.com"
and also a jupyter_config.json of:
{ "LabApp":{ "yarn_registry": "https://www.myregistry.com" }, "BaseExtensionApp":{ "yarn_registry": "https://www.myregistry.com" }, "LabBuildApp":{ "yarn_registry": "https://www.myregistry.com" } }

but neither seem to work