[roll] Roll fuchsia [assembly] Multi-product builds have empty amber-files

This is necessary for some test shards.

Original-Bug: 395937765
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1210304
Original-Revision: 85c941ffce75af8344bd0bc0a3ea4e1cc143ee7a
GitOrigin-RevId: 471b9c01695f3772a253c5446ef7ea19593e84c9
Change-Id: I23300fcfe2b02101cfc5b75deaf26d83a4b0a5fb
diff --git a/stem b/stem
index e25fb29..a30273e 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="8e7a3d929eaa8da43cb1857435a914f7590f7271"/>
+             revision="85c941ffce75af8344bd0bc0a3ea4e1cc143ee7a"/>
   </projects>
   <hooks>
     <hook name="install-environment"