Stop relying on target.kind in mixed builds.

target.kind was a field that existed for only a few months, and have
been removed from Bazel. This is needed to update to a newer Bazel version.

Also, this reverts filegroups to be queried for a specific arch again,
but leaving file targets in the common arch (which is correct, anyway).

Fixes: b/199363072
Test: mixed_libc
Test: presubmits
Change-Id: I3b8e5c43a39516d977d327a44a75750b2f251be3