buildbot_test_toolchains: fix a typo

BUG=none
TEST=it runs with a patch parameter.

Change-Id: I08437d0ec47ef27a3b88930358f3c149fd955cdc
Reviewed-on: https://chrome-internal-review.googlesource.com/227861
Reviewed-by: Han Shen <shenhan@google.com>
Commit-Queue: Yunlian Jiang <yunlian@google.com>
Tested-by: Yunlian Jiang <yunlian@google.com>
diff --git a/buildbot_test_toolchains.py b/buildbot_test_toolchains.py
index a54fa0f..8e4cf2d 100755
--- a/buildbot_test_toolchains.py
+++ b/buildbot_test_toolchains.py
@@ -273,7 +273,7 @@
 
   if options.patches:
     global USE_NEXT_GCC_PATCH
-    USE_NEXT_GCC_PATCH = options.patch.split(',')
+    USE_NEXT_GCC_PATCH = options.patches.split(',')
 
   fc = ToolchainComparator(options.board, options.remote,
                            options.chromeos_root, options.weekday)