[Linux] Set permission for gdb to attach

[Linux] Set permission for gdb to attach

Most modern Linux distributions limit the ptrace scope to allow
attaching only to the direct child processes for security reasons. The
user on such machine has to modify sysctl in order to allow non-root
processes to attach to arbitrary processes, which opens up a potential
security issue. The alternative is what's implemented here - when we
crash and ask gdb to dump the stack we can bless the gdb process and allow
it to attach to our process using prctl(2)