authfs: Re-enable the build of device unit test

The build rule was removed due to broken presumit on Tree Hugger. This
change only re-enable the build rule without adding TEST_MAPPING.

Test: atest
Bug: 173507504
Change-Id: Iadc8cd6074140185ecd3ae3db017c7f1573f5f4e
diff --git a/authfs/Android.bp b/authfs/Android.bp
index 225ff40..9808bf6 100644
--- a/authfs/Android.bp
+++ b/authfs/Android.bp
@@ -51,7 +51,7 @@
 
 // TODO(victorhsieh): Enable the test once "undefined symbol: _Unwind_Resume" is fixed, then add to
 // TEST_MAPPING.
-//rust_test {
-//    name: "authfs_device_test_src_lib",
-//    defaults: ["authfs_defaults"],
-//}
+rust_test {
+    name: "authfs_device_test_src_lib",
+    defaults: ["authfs_defaults"],
+}