[testsuite] don't use lto plugin if it doesn't work

[Mike Stump]

On Jun 28, 2012, at 3:19 PM, Alexandre Oliva wrote:
> On Jun 28, 2012, Mike Stump <mikestump@comcast.net> wrote:
>> The next would be because it would be a speed hit to re-check at
>> runtime the qualities of the linker and do something different.
> 
> But then, our testsuite *does* re-check at runtime, but without my
> patch, we're not using completely the result of the test.

Hum, we're not making progress in the conversation.  Let me reboot it.  First, let get to the heart of the matter.  That is the behavior of compiler.  Do you think it works perfectly and needs no changing in this area, or if not, what changes do you want?

My take was, the compiler should not try and use the plugin that won't work, and that this should be a static config bit built up from the usual config time methods for the host system.  Do you agree, if not why, and what is your take?