Avoid downloading GMS & Support repositories

[juandiana]

This is perhaps a "feature request".

We use a local Maven repository for our Android build. In it we have all our dependencies. So we would like to avoid downloading the Google Play Services & Android Support repositories.

Looking at the source code, I see it assumes that the build takes its dependencies from the Maven repositories provided by the Android SDK Manger since it checks for the existence of these directories.

It would be nice if we could avoid this, for instance, by setting a flag in the build.gradle file.

sdkManager {
  checkGMSRepository false
  checkSupportRepository false
}