apex: Add prepare_device_vfio script

'prepare_device_vfio.sh' prepares a device for VFIO assignment by
binding a VFIO platform driver, configuring VFIO framework, and
verifying the resulting directory structure. This must be done before
the device is passed to crosvm for further handling and assignment to a
VM.

This is a temporary helper before properly implementing management of
assignable devices in virtualizationservice.

Test: Run 'prepare_device_vfio.sh <DEVICE_NAME>', then verify device
driver name.

Change-Id: I3026723913999ed4d98d4e9bba4a996f38cbed42
diff --git a/apex/Android.bp b/apex/Android.bp
index fedcfcd..7ef2c79 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -106,6 +106,7 @@
     ],
     host_required: [
         "vm_shell",
+        "prepare_device_vfio",
     ],
     apps: [
         "EmptyPayloadApp",
@@ -136,6 +137,12 @@
     installable: false,
 }
 
+sh_binary_host {
+    name: "prepare_device_vfio",
+    src: "prepare_device_vfio.sh",
+    filename: "prepare_device_vfio.sh",
+}
+
 // Virt apex needs a custom signer for its payload
 python_binary_host {
     name: "sign_virt_apex",