The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/c710f884e8971465a4f204e07cce225bf7039c06

commit c710f884e8971465a4f204e07cce225bf7039c06
Author: Yunlian Jiang <yunlian@google.com>
Date: Thu Nov 10 22:24:26 2016

profile: Disable USE="clang" for llvm.

We want to pass USE flags to update_chroot.
For llvm-next buildbot, the USE flag is "clang llvm-next".
Currently we do not want to use clang to build llvm. So
we need to remove the USE="clang" support from the ebuild file.

BUG= chromium:663784 
TEST=sudo USE="clang" emerge llvm finishes.

Change-Id: I23a1ecd422b9d0be89745eaefc7816e473c294f2
Reviewed-on: https://chromium-review.googlesource.com/410141
Commit-Ready: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[add] https://crrev.com/c710f884e8971465a4f204e07cce225bf7039c06/profiles/targets/sdk/package.use.mask

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/4c32a0abb9d9e1884176132ecd1698c8ad1713a6

commit 4c32a0abb9d9e1884176132ecd1698c8ad1713a6
Author: Yunlian Jiang <yunlian@google.com>
Date: Thu Nov 10 21:32:17 2016

chromeos_config: set latest_toolchain=True for llvm-next

BUG= chromium:663784 
TEST=the --nousepkg flag is passed to update_chroot.
     for arm-llvm-next-toolchain.

Change-Id: I6d925ac5705887c9ab6a30ac7d75d0db8098de3a
Reviewed-on: https://chromium-review.googlesource.com/410161
Commit-Ready: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>

[modify] https://crrev.com/4c32a0abb9d9e1884176132ecd1698c8ad1713a6/cbuildbot/config_dump.json
[modify] https://crrev.com/4c32a0abb9d9e1884176132ecd1698c8ad1713a6/cbuildbot/chromeos_config.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/f72427c1c6b083973f07352190872962b7137b71

commit f72427c1c6b083973f07352190872962b7137b71
Author: Yunlian Jiang <yunlian@google.com>
Date: Wed Nov 09 19:24:52 2016

cbuildbot: pass extra_env to UpdateChroot.

This passes extra_env to UpdateChroot in
SetupBoardStage.

BUG= chromium:663784 
TEST=USE="llvm-next" is added to update_chroot command line.
     when running arm-llvm-next-toolchain buildtbot.

Change-Id: I29187a191ab4fd305c9cfa7939b8aadde710558f
Reviewed-on: https://chromium-review.googlesource.com/409059
Commit-Ready: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>

[modify] https://crrev.com/f72427c1c6b083973f07352190872962b7137b71/cbuildbot/stages/build_stages.py