Make gather-topology report debug info on all OS

[bgoglin]

We have hwloc-gather-topology (script that gathers a sysfs/proc tarball on Linux and runs lstopo) and hwloc-gather-cpuid (C file that gathers cpuid files without building a tarball). We should merge and/or uniformize all this.

Ideas:

• Keep gather tools separated but have gather-cpuid make a tarball and run lstopo too.
• Call gather-cpuid from gather-topology on x86, and tarball everything including cpuid. Will require to extend gather-topology to non-Linux even if it does pretty much nothing except cpuid there.

[bgoglin]

Now that gather-topology calls gather-cpuid on x86, we may want to allow gather-topology on all OS, not only on Linux. At least is should do gather-cpuid on x86, but it could also gather the debugging info that we request in bug reports (see https://github.com/open-mpi/hwloc/blob/master/.github/issue_template.md)