talked to firmware team, it at least includes:
    coreboot
    depthcharge
    libpayload
    vboot_reference
    coreinfo
    chromeos-bootimage
    chromeos-seabios
    chromeos-u-boot
    coreboot-private-files-*
    chromeos-cr50
    chromeos-ec
    chromeos-mrc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9

commit 98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9
Author: Yunlian Jiang <yunlian@chromium.org>
Date: Fri Aug 26 17:25:33 2016

profile: use gcc to build firmware.

We need to continue to use gcc to build firmware while we are
migrating to LLVM. Talked to firmware team and they gave us
a list of firmware packages.

BUG= chromium:641388 
TEST=these packages will continue to be built with gcc.

Change-Id: I0eb6cd57ee74df7005a67667e340bd29fddad4e6
Reviewed-on: https://chromium-review.googlesource.com/376758
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/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/chromeos-base/chromeos-cr50
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/sys-boot/coreboot
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/sys-boot/chromeos-u-boot
[modify] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/chromeos-base/vboot_reference
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/sys-boot/libpayload
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/chromeos-base/chromeos-ec
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/sys-boot/coreinfo
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/sys-boot/chromeos-bootimage
[add] https://crrev.com/98b29a9f5ac313cb719ceea8c1df674bf7fdf5e9/chromeos/config/env/sys-boot/depthcharge