Developer portal is not using relative path while loading static contents like cs, js and media

[pophitu]

I am exposing apim developer portal through Frontdoor with path-based routing.

Any traffic will come with /apimdev/* will forward to apim developer portal.
Above setup is working without problem. However, this developer portal is MS managed application. Once main html comes to browser, to load other static contents, like js, css, images etc, browser is not using the relative path.
Example, https://abc.azurefd.net/apimdev/ is loading, if you see the page source, there is js file which ideally should be loaded using https://abc.azurefd.net/apimdev/scripts/theme.js, rather browser is trying to load from https://abc.azurefd.net/scripts/theme.js (using the default route)
This explains that the way developer portal is constructed, is not using relative path.
Currently, the default route of the Frontdoor is set to another portal which we dont want to change.