cros_setup_toolchains: Add eclass-overlay to list of chroot overlays

BUG=brillo:1113
TEST=`./update_chroot`

Change-Id: I8bcfde2b57262bd1ee0bf4d008d19ffba4bd123b
Reviewed-on: https://chromium-review.googlesource.com/274717
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
Tested-by: Christopher Wiley <wiley@chromium.org>
diff --git a/scripts/cros_setup_toolchains.py b/scripts/cros_setup_toolchains.py
index 237acb2..fa4fd48 100644
--- a/scripts/cros_setup_toolchains.py
+++ b/scripts/cros_setup_toolchains.py
@@ -37,6 +37,7 @@
 SRC_ROOT = os.path.realpath(constants.SOURCE_ROOT)
 
 CHROMIUMOS_OVERLAY = '/usr/local/portage/chromiumos'
+ECLASS_OVERLAY = '/usr/local/portage/eclass-overlay'
 STABLE_OVERLAY = '/usr/local/portage/stable'
 CROSSDEV_OVERLAY = '/usr/local/portage/crossdev'
 
@@ -144,7 +145,7 @@
                       '-P', '--usepkgonly',
                       '--without-headers'])
 
-    overlays = '%s %s' % (CHROMIUMOS_OVERLAY, STABLE_OVERLAY)
+    overlays = ' '.join((CHROMIUMOS_OVERLAY, ECLASS_OVERLAY, STABLE_OVERLAY))
     cmdbase.extend(['--overlays', overlays])
     cmdbase.extend(['--ov-output', CROSSDEV_OVERLAY])