[LTP] [PATCH 1/1] README: Document gdb debugging

[Petr Vorel]

Hi Cyril,

...
> > +Debugging with gdb
> > +==================
> > +
> > +To get stack trace of a crashing test in gdb it's useful to
> > +[`set follow-fork-mode child`](https://ftp.gnu.org/old-gnu/Manuals/gdb/html_node/gdb_25.html).

> Maybe we should start with a sentence that actually describes how things
> are organized so that it's clear why this is needed. Maybe just:

> The new test library runs the actual test, i.e. the `test()` function in
> a forked process. To get the stack trace of a crashing test it's needed
> to [`set ....

+1, thank you.

Kind regards,
Petr