[stdlib] use “LifetimeDependenceMutableAccessors”

Author: glessard

stdlib/cmake/modules/SwiftSource.cmake

@@ -636,6 +636,7 @@ function(_compile_swift_files
   list(APPEND swift_flags "-enable-experimental-feature" "NonescapableTypes")
   list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependence")
   list(APPEND swift_flags "-enable-experimental-feature" "InoutLifetimeDependence")
+  list(APPEND swift_flags "-enable-experimental-feature" "LifetimeDependenceMutableAccessors")
 
   list(APPEND swift_flags "-enable-upcoming-feature" "MemberImportVisibility")