Add minimal UART driver for console.

Bug: 223166344
Test: Ran unprotected VM under crosvm.
Change-Id: I4e779ab0c87597db9384247f269b2b28f6e18b30
diff --git a/pvmfw/Android.bp b/pvmfw/Android.bp
index 7123da4..ce096b6 100644
--- a/pvmfw/Android.bp
+++ b/pvmfw/Android.bp
@@ -8,6 +8,9 @@
         "libcompiler_builtins.rust_sysroot",
         "libcore.rust_sysroot",
     ],
+    rustlibs: [
+        "libspin_nostd",
+    ],
     enabled: false,
     target: {
         android_arm64: {