This is a failure we noticed on FreeBSD. I thought I reported it
earlier, but maybe not.
In src/topology-freebsd.c, the definition and usage of
hwloc_freebsd_node_meminfo_info() need to be protected by both
HAVE_SYSCTL and HAVE_SYS_SYSCTL_H (currently it's only protected by
HAVE_SYSCTL). The former provides the declaration for the function and
the latter provides the macros used within the definition of the
function (e.g., CTL_HW).
I hope this is a small enough patch to make it into 1.7.1 GA.