chromite: Fix typo in error message

Spell unknown correctly.

BUG=None
TEST=None

Change-Id: I096ad6b81d9d71ce13d5328d1628f4d86003818b
Reviewed-on: https://chromium-review.googlesource.com/1584230
Commit-Ready: Stephen Boyd <swboyd@chromium.org>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Philip Chen <philipchen@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index c59421d..b694539 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -653,7 +653,7 @@
 
   # Ensure that all args are legitimate config targets.
   if options.build_config_name not in site_config:
-    cros_build_lib.Die('Unkonwn build config: "%s"' % options.build_config_name)
+    cros_build_lib.Die('Unknown build config: "%s"' % options.build_config_name)
 
   build_config = site_config[options.build_config_name]
   is_payloads_build = build_config.build_type == constants.PAYLOADS_TYPE