Fix gyp part two: fix harder

Having mojo_application_bindings export the dependent setting on
mojo_application_bindings_mojom causes duplicate symbol errors on
android and mac, so instead export the setting from
mojo_application_base.

Try runs here: https://codereview.chromium.org/726933006/

R=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/730763002