Enable bootstrap test in CI

Adds testing a bootstrap with RSA/ECDSA signing and KW encryption.

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/sim/mcuboot-sys/Cargo.toml b/sim/mcuboot-sys/Cargo.toml
index 09b323b..16cc8d5 100644
--- a/sim/mcuboot-sys/Cargo.toml
+++ b/sim/mcuboot-sys/Cargo.toml
@@ -29,6 +29,9 @@
 # Encrypt image in slot1 using AES-KW-128
 enc-kw = []
 
+# Allow bootstrapping an empty/invalid slot0 from a valid slot1
+bootstrap = []
+
 [build-dependencies]
 cc = "1.0.25"