PATCH: Add x32 dummy sysctl

[Roland McGrath]

> X32 doesn't have _sysctl system call.  This patch adds a dummy.  OK
> to install?

Then you shouldn't install <sys/sysctl.h> either.  Since these are added to
sysdep_routines and sysdep_headers in sysdeps/unix/sysv/linux/Makefile and
a linux/x32-specific Makefile would be before it, I think what you need to
do is set some variable in linux/x32/Makefile to say there's no sysctl and
then have linux/Makefile check that.

That's hacky, but it's better than moving the settings into copies
in every other linux/<machine>/Makefile.

Alternatively and arguably cleaner though a little less obvious:
move those additions from linux/Makefile into linux/sysctl.mk
and give linux/Makefile:

include $(firstword $(wildcard $(sysdirs:=/sysctl.mk)))

Then you can add a linux/x32/sysctl.mk to override linux/sysctl.mk
with a dummy.

I like the latter one better.  It certainly needs thorough comments.


Thanks,
Roland