vmm: Introduce landlock cmdline parameter

Users can use this cmdline option to enable/disable Landlock based
sandboxing while running cloud-hypervisor.

Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>

vmm/src/vm_config.rs

@@ -645,4 +645,6 @@ pub struct VmConfig {
     // valid, and will be closed when the holding VmConfig instance is destroyed.
     #[serde(skip)]
     pub preserved_fds: Option<Vec<i32>>,
+    #[serde(default)]
+    pub landlock_enable: bool,
 }