Fix out/soong/Android-<>.mk reproducibility

When there were multiple modules overriding a single module, sometimes
we would create the list in different orders, which would trigger some
of the later mutators to write the Android-<>.mk out in different
orders.

Bug: 160207422
Test: diff out/soong/Android-<>.mk between multiple runs on internal master
Change-Id: I321db706dd34aa20a0b1556fd282d54b826a4a97