Merge "rust: Migrate default edition to 2021" am: c207773056

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1920524

Change-Id: Iee94c8ee0f7cc2da511aaeee315c6ac1451a71d3
diff --git a/rust/config/global.go b/rust/config/global.go
index 2821e31..bfb2d1f 100644
--- a/rust/config/global.go
+++ b/rust/config/global.go
@@ -26,7 +26,7 @@
 var (
 	RustDefaultVersion = "1.57.0"
 	RustDefaultBase    = "prebuilts/rust/"
-	DefaultEdition     = "2018"
+	DefaultEdition     = "2021"
 	Stdlibs            = []string{
 		"libstd",
 	}