cros_setup_toolchain: Add coreboot-sdk to post-cross

This ensures that they're installed from binpkgs, not from source.
coreboot-sdk takes a really long time to build and therefore shouldn't
have to be rebuilt on every workstation (in the worst case).

BUG=chromium:933284
BRANCH=none
TEST=update_chroot installs coreboot-sdk from binary

Change-Id: I6f7c13f553522670ba4720d435afd68d1313eca2
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1479990
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
diff --git a/scripts/cros_setup_toolchains.py b/scripts/cros_setup_toolchains.py
index a3fe06a..ba5dda4 100644
--- a/scripts/cros_setup_toolchains.py
+++ b/scripts/cros_setup_toolchains.py
@@ -70,6 +70,7 @@
     'dev-lang/rust',
     'dev-util/cargo',
     'virtual/target-sdk-post-cross',
+    'dev-embedded/coreboot-sdk',
 )
 
 # New packages that we're in the process of adding to the SDK.  Since the SDK