OWNERS.build: add Stephane

BUG=None
TEST=upload still works

Change-Id: Ifc4a088a1bba975321adb049d4d22f504d664047
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2332690
Reviewed-by: Stephane Belmon <sbelmon@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/OWNERS.build b/OWNERS.build
index 8f1f081..d952138 100644
--- a/OWNERS.build
+++ b/OWNERS.build
@@ -6,6 +6,7 @@
 cjmcdonald@chromium.org
 mmortensen@google.com
 saklein@chromium.org
+sbelmon@google.com
 vapier@chromium.org
 
 # COMPONENT: Infra>ChromeOS>Build