How to use proxyUrls for local builds, but not for deployment?

I have setup a proxyUrl for external API to avoid CORS issues when running locally, as described in:

However, when I attempt to deploy the app as a cordova build (for example, as an APK) for testing on devices, the proxy URL’s are no longer relevant (they are file:// on device).

How can I adjust my build scripts or code so that

$ ionic cordova build android

ignores the proxyUrls and instead uses a real URL?