sim: Test software rollback protection

Signed-off-by: Håkon Øye Amundsen <haakon.amundsen@nordicsemi.no>
Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/sim/mcuboot-sys/Cargo.toml b/sim/mcuboot-sys/Cargo.toml
index 3466ff0..cbf05e5 100644
--- a/sim/mcuboot-sys/Cargo.toml
+++ b/sim/mcuboot-sys/Cargo.toml
@@ -47,6 +47,9 @@
 # Support multiple images (currently 2 instead of 1).
 multiimage = []
 
+# Check (in software) against version downgrades.
+downgrade-prevention = []
+
 [build-dependencies]
 cc = "1.0.25"