make 3rd-party tools available w/out explicit packages

We don't need to hide the tools if no packages are opted in.
This way we can still get `emerge` when requested and then we
can run it by hand.

TEST=default build doesn't include any tools
TEST=adding 3rd-party-packages to PRODUCT_PACKAGES includes tools only
TEST=also adding PRODUCT_3RD_PARTY_PACKAGES includes those packages

Change-Id: I59a9eea6a6b3e0f15b0ca076be36340c786021e5
1 file changed