Comment # 30 on bug 1040589 from Martin Li��ka

Function timeval_to_cpu should clearly be marked with
no_profile_instrument_function attribute
as number of loop iterations depends on time.

The other differences are in string functions, very hard to tell what's the
difference.
But as we know any of these can potentially cause a code generation difference.

Last topic we discussed are -fprofile-values counters. There can really diverge
when running a parallel
test-suite. It would be possible to resolve in GCC 10.