qemu-ga: Introduce Windows MSI script

The script enables building Windows MSI installation package on Linux with wixl tool.

Signed-off-by: Yossi Hindin <yhindin@redhat.com>
Message-Id: <1430913460-13174-4-git-send-email-yhindin@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>