vmTools: use modules output from kernel (#434414)

pkgs/build-support/vm/default.nix

···
   qemu = buildPackages.qemu_kvm;
 
   modulesClosure = pkgs.makeModulesClosure {
-    inherit kernel rootModules;
+    kernel = lib.getOutput "modules" kernel;
+    inherit rootModules;
     firmware = kernel;
   };