Enable automated marshalling for the syscall package.

PiperOrigin-RevId: 331940975

pkg/sentry/kernel/auth/BUILD

@@ -57,6 +57,7 @@ go_library(
         "id_map_set.go",
         "user_namespace.go",
     ],
+    marshal = True,
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/abi/linux",

pkg/sentry/kernel/auth/id.go

@@ -19,9 +19,13 @@ import (
 )
 
 // UID is a user ID in an unspecified user namespace.
+//
+// +marshal
 type UID uint32
 
 // GID is a group ID in an unspecified user namespace.
+//
+// +marshal slice:GIDSlice
 type GID uint32
 
 // In the root user namespace, user/group IDs have a 1-to-1 relationship with