dtc/.git file included in release tarball

The release tarballs include the dtc/.git submodule file, causing when working git in some circumstances (e.g. doing git clean -fxd in a parent git repository):

$ mkdir foo && cd foo
$ git init
$ echo yo >bar
$ curl http://wiki.qemu-project.org/download/qemu-1.6.0.tar.bz2
$ tar xjf qemu-1.6.0.tar.bz2
$ git clean -fxd
Removing bar
Removing qemu-1.6.0.tar.bz2
Removing qemu-1.6.0/
fatal: Not a git repository: qemu-1.6.0/pixman/../.git/modules/pixman

Leaving the qemu-1.6.0 directory intact.

So, my suggestion is, would it be possible to filter out the .git file from the release tarball when building a release? Thanks.