Flavour wise source set management in android

Question

In android project, we are currently having two different flavours Ex : USA and Canada. We are maintaining common "res" in main folder.

Now, we want to add one more flavour. Ex : Australia.

The problem arrived here. The Australia country flavour is should not have the main folder "res". So that we created one new folder "usaCanadaMain" and added all the common Java, assets and res files. Modified the source set as mentioned below.

sourceSets {
        main {
            java.srcDirs += ['src/main/java']
        }
        usa {
            java.srcDirs += ['src/usaCanadaMain/java']
            resources.srcDirs += ['src/usaCanadaMain/assets']
            main.res.srcDirs += ['src/usaCanadaMain/res']
        }
        canada {
            java.srcDirs += ['src/usaCanadaMain/java']
            resources.srcDirs += ['src/usaCanadaMain/assets']
            main.res.srcDirs += ['src/usaCanadaMain/res']
        }
        australia {
            resources.srcDirs += ['src/australia/assets']
        }
    }

While compiling australia flavour, "usaCanadaMain" res files also added.

Expectation : While compiling

1. While Australia flavour compilation, "usaCanadaMain" res should not added in main.
2. While USA and Canada flavour compilation, "usaCanadaMain" res should added in main.

What is the solution for this?? Any other alternative solution to handle this??