Proguard implicitly generates a proguard_dictionary

Use .KATI_IMPLICIT_OUTPUTS to convey as such.

This is to support a use case for building platform/art/tools/ahat,
which depends on the generated proguard_dictionary for running tests.

Test: m
Test: m ahat-test with relevant changes from clean build.
Change-Id: Ic8f3b6819cfd4cd18620a2eaafd80d672fde8f5c