vm: Use Structopt for parsing command line arguments

Test: adb shell /apex/com.android.virt/bin/vm --help
Change-Id: I1c19f6f3d0ef3f78cd1c8a52fbce6a09affe08fe
diff --git a/vm/Android.bp b/vm/Android.bp
index 5089e39..248af4d 100644
--- a/vm/Android.bp
+++ b/vm/Android.bp
@@ -14,6 +14,7 @@
         "libenv_logger",
         "liblibc",
         "liblog_rust",
+        "libstructopt",
     ],
     apex_available: [
         "com.android.virt",