Fix/clean-up the build for lmbench

[MarekBykowski]

This is the heads-up that meta-oe of Yocto is planning on integrating a couple of changes to lmbench.

These changes can be wrapped up around fixing/cleaning up as follows:

• if lmbench doesn't use a return from a function attributed to warn_unused_result supress the warning/s
• fix buffer overflow
• define feature_test_macro _GNUSOURCE compiling in sched{get,set}affinity()
• go strict for a pre-build check if sched_{get,set}affinity() from glibc builds cleanly. If it is not compile it out.

Please find the original discussion on the changes at meta-oe http://lists.openembedded.org/pipermail/openembedded-devel/2019-October/202206.html

I have tested these changes against this repo and they build just fine. The compiler warns though about the changes which already are in the meta-oe and are not part of this commit.

Signed-off-by: Marek Bykowski marek.bykowski@gmail.com Reviewed-off-by: Marcin Lapaj marcin.lapaj@tieto.com