Updating autogenerated Trusty makefile rules

Bug: 281857510
Change-Id: I5ea6bce575f0341b369b68e684a579f74dc1f510
diff --git a/rules.mk b/rules.mk
index ff3d072..af80af0 100644
--- a/rules.mk
+++ b/rules.mk
@@ -18,6 +18,6 @@
 	external/rust/crates/proc-macro-error-attr \
 	external/rust/crates/proc-macro2 \
 	external/rust/crates/quote \
-	external/rust/crates/syn \
+	external/rust/crates/syn/1.0.107 \
 
 include make/library.mk