Get rust from CIPD

The rust on corp systems is older than what PyOxidizer requires.

Change-Id: I1a952a5998b859fc3b387e67df1f6b11b769a2f5
diff --git a/env_setup/cipd/pigweed.ensure b/env_setup/cipd/pigweed.ensure
index 34a83b7..241c2c0 100644
--- a/env_setup/cipd/pigweed.ensure
+++ b/env_setup/cipd/pigweed.ensure
@@ -62,3 +62,6 @@
 
 # OpenOCD
 pigweed/third_party/openocd/${os=linux}-${arch} git_revision:646566e006acd58fb9ac405511d3ecca79f26d55
+
+# Rust
+fuchsia/rust/${platform} git_revision:caa231d998a5e853c7ba1455d7a05b500df9d63c