cros_setup_toolchains: add a post-cross-compiler set of packages

This is cherry-pick of following CL
https://chromium-review.googlesource.com/699064 with rust removed
and virtual/target-sdk-post-cross added.

BUG=b:162254118
TEST=precqs pass
CQ-DEPEND=CL:2478667

Change-Id: I71326e906723cc49e3d08efee98443e329756eb1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2478985
Tested-by: Patryk Duda <patrykd@google.com>
Commit-Queue: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>
1 file changed