you were not able to disable the header checks, so if the header was not
there it indicated that you could turn it of. However, the option check
was in the has_header if not outside of it. Further more, header checks
are done in the subdirectory that is done for header checks,
unneccessary cpu_**** flags are removed, global optimization options are
added to the global_arguments instead of just the package_c_args, which
leads to the fact that also all binaries etc. are build by default with
those optimization flags.
This also reduces the amount of options to a minimum of 1 option, to
just control if there should be the optimization or not.
Depends on D7295