scripts: dev_cli: Add --features option

Let's officially have a way to pass the features used to build
cloud-hypervisor to the dev_cli.sh script.

This doesn't invalidate the previous commit, as we still don't what the
features_build variable to be quoted, otherwise we face the following
issue:
```
error: Found argument '--features tdx' which wasn't expected, or isn't valid in this context
	Did you mean --features?

USAGE:
    cargo build --all --features <FEATURES>...
```

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

scripts/dev_cli.sh

@@ -241,6 +241,10 @@ cmd_build() {
             shift
             hypervisor="$1"
             ;;
+        "--features")
+            shift
+            features_build="--features $1"
+            ;;
         "--") {
             shift
             break