Add LOCAL_EXPORT_C_INCLUDE_DEPS

This shouldn't be necessary for most makefiles, since we add
$(LOCAL_GENERATED_SOURCES) to this already included, but for prebuilts
that aren't actually prebuilts (Soong modules), we need to pass
dependencies so that the generated headers are built before being used.

Bug: 31742855
Test: Use, inspect build-*.ninja
Change-Id: I8d9f675af639d3f40780d48a016fc079a82531c2