Use gen-libm-test.py to generate ulps table for manual

[Florian Weimer]

* Carlos O'Donell:

> On 08/13/2018 04:04 PM, Florian Weimer wrote:
>> * Carlos O'Donell:
>> 
>>> I'm impressed, you've done a really good job keeping this minimal, but what's
>>> the problem with including python here?
>> 
>> It would need a special bootstrap build, reducing external
>> dependencies to the bare minimum.  A typical distribution build of
>> Python pulls in X, Java and perhaps more.
>  
> You still haven't answered the "Why?"
>
> Why does your bootstrap need to be smaller?
>
> What is wrong with "typical?"

When we did this in Fedora, the bootstrap set was pretty much the
whole distribution, so fully bootstrapped builds are extremely rare
and generally happen only during architecture bringup, and often not
even then.

Andreas' setup is very good for detecting certain types of build
issues, and I wouldn't want to lose that.