[PATCH] Add syscall tests when following/detaching from fork

[PATCH] Add syscall tests when following/detaching from fork

breakpoints/13457 discusses issues with syscall catchpoints when
following forks, lamenting that there is no coverage for the
various permutations of `follow-fork-mode' and `detach-on-fork'.

This is an attempt to try and cover some of this ground. Unfortunately
the state of syscall support when detaching after the fork is
very, very inconsistent across various architectures. [I've tested
extensively Fedora/RHEL platforms.]

Right now, the only reliable platform to run tests on is x86_64/i?86
for the specific case where we do not detach from the fork. Consequently,
this patch limits testing to those architectures.

I have updated breakpoints/13457 with my findings on failures with the
detaching case.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=13457
Approved-By: Andrew Burgess <aburgess@redhat.com>