qemu: add meta.mainProgram

pkgs/applications/virtualization/qemu/default.nix

@@ -283,6 +283,7 @@ stdenv.mkDerivation rec {
     homepage = "http://www.qemu.org/";
     description = "A generic and open source machine emulator and virtualizer";
     license = licenses.gpl2Plus;
+    mainProgram = "qemu-kvm";
     maintainers = with maintainers; [ eelco qyliss ];
     platforms = platforms.unix;
   };