[build2] Fix build on older x86 and arm CPUs

[Norbert Lange]

2018-01-01 12:34 GMT+01:00 Boris Kolpackov <boris at codesynthesis.com>:
> Norbert Lange <nolange79 at gmail.com> writes:
>
>> Again, why is this an issue, is there any measured performance implication?
>> [...]
>>
>> If there is much contention to affect perfromance, you need to look at
>> what you are doing [...]
>>
>> Can't tell anything without analyzing your whole code [...].
>
> This discussion is getting a bit tangential...

Indeed, there so much headaches when it comes to creating a
buildsystem that I don`t think
such optimizations are a big roadblock

> ... so for now I've added the macro
> (BUILD2_ATOMIC_NON_LOCK_FREE) to suppress lock-free checks. With that and by
> passing -latomic via LIBS (for bootstrap.gmake) and config.cc.loptions you
> should be able to link libatomic for platforms that need it. But let me know
> if something doesn't work with this approach.

I dont expect any trouble as soon as the #error is gone

Norbert