build-binutils.py: Do not build texinfo docs

[dileks]

As a desired wish from #221:

This requires on my system to install texinfowhich ships makeinfo to generate (tex)info doc files...

$ LANG=C LC_ALL=C ./build-binutils.py -t x86_64-linux-gnu

root# apt-get install -t unstable --no-install-recommends texinfo -y

...otherwise the build breaks.

For a fast toolchain build I wish an option like --no-docs to suppress the building and installing these doc files.
This saves build-time and disc-usage.

[nathanchance]

I just looked at the binutils configure file and I do not see any way to disable building the documentation so I am not really sure there is anything build-binutils.py can do about that. Perhaps this would be a better request for binutils upstream?

[dileks]

AFAICS some projects like Freetz router project carry patches to binutils...
...but I must check.

[dileks]

https://github.com/Freetz/freetz/blob/master/toolchain/make/target/binutils/2.26/005-no_docs__no_nls.patch