[.gitignore] please add generated file to .gitignore

[Alexander Aring]

On Thu, Dec 05, 2013 at 11:38:46AM +0800, Kevin Du Huanpeng wrote:
> I clone the code yesterday, maybe today for you.
> git clone git://git.pengutronix.de/git/barebox.git
> When I invoke
>  git cherry-pick 2bd891b0ae266bd7cac58805092fc3f4ae67e55e
> I can see  `fix_size kernel-install ` in script/.gitignore.
> Maybe it still not merged to master now yet.
> 

exactly, but that's okay Sascha isn't superman and I don't want to rush
him to merge it into master.

And me... I am just a linux guru with no special force to bring this
patch into master.

- Alex