fix OWNERS path

The find owners module will use the path in the current repo as the
implicit prefix even when crossing repo boundaries, so make sure we
have an explicit / anchor when loading from chromite.  It doesn't
make a difference in this repo, but might as well avoid copy & paste
confusion.

BUG=None
TEST=find owners can find owners for this

Change-Id: I951d477de7a9a93d01fd828fb69be25a5adec563
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/portage_tool/+/2336190
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Stephane Belmon <sbelmon@google.com>
Commit-Queue: Stephane Belmon <sbelmon@google.com>
diff --git a/OWNERS b/OWNERS
index 9cfd3fb..995488c 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1 +1 @@
-include chromiumos/chromite:OWNERS.build
+include chromiumos/chromite:/OWNERS.build