[roll] Roll fuchsia [rbe] Alert user if RBE overrides are found in env

Most RBE settings exist in config files, but reclient tools
honor `RBE_*` environment variables as flag-overrides.

Most users shouldn't be overriding these variables.
Overriding these could cause any number of issues,
so notify the user when these are seen.

Original-Bug: 415368631
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1267164
Original-Revision: 45d87cb144118f9904634cec211064ccb58a3bbc
GitOrigin-RevId: ef20105d5d11d440cba1301f860b05e5bf92c698
Change-Id: I4124bdc4f9a9889eb3ed881836d08393353cd8fb
diff --git a/stem b/stem
index db868e6..a5042c1 100644
--- a/stem
+++ b/stem
@@ -8,7 +8,7 @@
              root=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="966aa7e3a2622c23a1e6c2e9d21958df4c6b7e98"
+             revision="45d87cb144118f9904634cec211064ccb58a3bbc"
              />
   </imports>
   <projects>