build timestamps don't work

[Antony Pavlov]

Hi!

  I have found that on my Debian testing build system generation of
timestamps don't work correctly.

$ cd barebox.git
$ git checkout next
$ make mrproper
$ make qemu-malta_defconfig
$ make
$ cat .version
0
$ edit ...
$ edit ...
$ edit ...
$ make
$ cat .version
0
$ echo 4 > .version
$ make
$ edit ...
$ edit ...
$ edit ...
$ make
$ cat .version
4

-- 
Best regards,
  Antony Pavlov