[PR lto/41528] Add internal documentation in doc/lto.texi

[Ralf Wildenhues]

Hello,

* Diego Novillo wrote on Mon, Nov 15, 2010 at 07:23:15AM CET:
> +optimized builds.  A, perhaps surprising, side effect of this feature
> +is that any mistake in the toolchain that leads to LTO information not
> +being used (e.g. an older @code{libtool} calling @code{ld} directly).
> +This is both an advantage, as the system is more robust, and a
> +disadvantage, as the user is not informed that the optimization has
> +been disabled.

Well, such a disadvantage could be ameliorated with a warning, no?

Rainer just mentioned other instances where LTO would silently not do
TRT (nm in PATH with different format, etc), so it would seem generally
useful to at least optionally warn.

Thanks,
Ralf