I'd like to make shared_library() on Android export JNI_OnLoad only by default

[Andrew Grieve]

And I'm wondering if there are any objections to this approach (as there appear to have been two years ago)

Specifics in: https://codereview.chromium.org/2633593004/

In short, it's a change to the default, but targets can opt-out by removing the default config.