Nightly: in case of conflicts, add "our" changes on top

.github/push_artifacts.sh

@@ -30,6 +30,6 @@ i=0
 while [ $i -le 10 ] && ! git push --quiet --set-upstream origin "${BRANCH}"
 do
     sleep $[ ( $RANDOM % 32 )  + 1 ]s
-    git pull --rebase origin "${BRANCH}"
+    git pull --rebase origin --strategy-option ours "${BRANCH}"
     i=$(( $i + 1 ))
 done