Enable GPU in crosvm

When the GPU feature is turned on in crosvm, these modules are added as
dependencies. Since crosvm is included in the virt APEX, add the APEX to
the apex_available properties of the modules to make them available in
the APEX.

Android.bp

@@ -53,6 +53,10 @@ cc_library_headers {
     host_supported: true,
     defaults: ["libdrm_defaults"],
     export_include_dirs: ["include/drm", "android"],
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.virt",
+    ],
 }
 
 // Library for the device