Use .KATI_IMPLICIT_OUTPUTS in build/make/core/Makefile

There were still two places where we weren't using it. There may be
more, but these are the ones that come up with aosp_cf_x86_phone.

Test: m out/target/product/vsoc_x86/root/default.prop
Test: m out/target/product/vsoc_x86/obj/NOTICE_VENDOR.txt
Change-Id: I17671ca2ed60332aed2bf76aa00e42a92661b58a