sim: enable saving encrypted TLV for ECIES

This changes the simulator to save the encryption TLV itself instead
of the unecrypted AES-128 key when doing the ECIES encryption test,
to add proper test coverage of this configuration option.

Signed-off-by: Fabio Utzig <utzig@apache.org>

sim/mcuboot-sys/build.rs

@@ -178,6 +178,7 @@ fn main() {
         conf.define("MCUBOOT_ENCRYPT_EC256", None);
         conf.define("MCUBOOT_ENC_IMAGES", None);
         conf.define("MCUBOOT_USE_TINYCRYPT", None);
+        conf.define("MCUBOOT_SWAP_SAVE_ENCTLV", None);
 
         conf.file("../../boot/bootutil/src/encrypted.c");
         conf.file("csupport/keys.c");