Strengthen ICF hash

[Joseph Myers]

On Wed, 4 Mar 2015, Jan Hubicka wrote:

> But yes, I do not think we need to significantly slow things down in current
> implemetnation when this feature does not work.  Just perhaps keep track of
> changes that introduce host specific stuff and not introduce these when it is
> easily avoidable.

Known LTO host dependencies are listed in bug 41526, so I suggest listing 
any new such host dependencies there (and noting there if anything listed 
is in fact now fixed).

-- 
Joseph S. Myers
joseph@codesourcery.com