add swarming prebuilt

it is handy from time to time

Change-Id: Id600cfa547e81806ee83efc0d782fda352fe8b2c
Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/prebuilt/+/382234
Reviewed-by: Marc-Antoine Ruel <maruel@google.com>
diff --git a/cipd.ensure b/cipd.ensure
index 6d08705..3b8b6f3 100644
--- a/cipd.ensure
+++ b/cipd.ensure
@@ -32,6 +32,9 @@
 # Lucicfg tool
 infra/tools/luci/lucicfg/${platform}  git_revision:5430afa7bbcd53f53f49075b65dc1fca0737c117
 
+# swarming
+infra/tools/luci/swarming/${platform} git_revision:729d131dbec2819048fda775bf4a25b70dd1252f
+
 # vpython
 infra/tools/luci/vpython/${platform} git_revision:5430afa7bbcd53f53f49075b65dc1fca0737c117