Add the list of makefiles that were also included by product config to dumpconfig.

In this entry, the first list of files is the inherit-product stack, and
the second one is the list of files included by the file at the top of
the stack that just finished processing

Test: build/make/ci/dump_product_config
Change-Id: I826b1ec6fa1319b8f0cdfaacc6ccf999ce93d9f1