Report the name of ptrace command when ptrace_attach_or_seize fails.
Report the name of ptrace command when ptrace_attach_or_seize fails.

* strace.c (ptrace_attach_cmd): New variable.
(ptrace_attach_or_seize): Save last ptrace command's name
to ptrace_attach_cmd.
(attach_tcb, startup_child): Use it in error diagnostics.

Saruta/strace,cuviper/strace,cuviper/strace,Saruta/strace,Saruta/strace,cuviper/strace,Saruta/strace,Saruta/strace,cuviper/strace,cuviper/strace