Make LTO Patch for Job Server Thread Detection Agnostic

[Paul Smith]

On Thu, 2020-02-27 at 16:58 +0000, Jonathan Wakely wrote:
> > That's a problem then as were assuming a user's build system for this
> > to work. I mean for now its fine but in the future wouldn't it de a
> > good ideal to not assume this?
> 
> It works fine for everybody. There's just an optimisation for people
> with a GNU make jobserver available. I don't see a problem.
> 
> If somebody wants to add an optimisation for their preferred build
> system they can propose a patch.

And/or they can suggest to other build systems that they also add support
for this service.

I'm not aware of any service like this which is supported by all build
tools, so it's not like we're choosing this over something else that's more
widely available.  Actually as far as I know other build tools don't
provide anything like it, portable or not.