Fix: build error when a lib with stubs is included in an APEX

apex { name: "foo", native_shared_libs: ["mylib"] }
cc_library { name: "mylib", shared_libs: ["other_lib"],
             stubs: { versions: ["1"]}, }

This is causing build error due to missing variant for other_lib.
This is happening because the stubs variant of mylib is added to apex
foo instead of the non-stubs variant. Because stubs variant does not
have any further dependencies, other_lib is not included to the APEX and
is not built for it.

Fixing this issue by specifying the version variant when adding a lib to
the dependency of an APEX, so that non-stub variant of the lib is
depended on.

Test: m (apex_test updated)
Change-Id: I972b6dcbce11942f83a76212715ba915534ec3df