Soong works with empty VNDK version

This change is to fix more misc issues to enable Soong without VNDK
version. This change contains

* Update properties in generated Android.mk
* Update VNDK APEX build to work without VNDK version

Bug: 316829758
Test: AOSP Cuttlefish build succeeded
Change-Id: I10f3c798299afe2d539ec3426b8e2b6068a158f6