[PATCH v2] Improve ptrace-error detection on Linux targets

[Eli Zaretskii]

> Cc: Eli Zaretskii <eliz@gnu.org>, Ruslan Kabatsayev <b7.10110111@gmail.com>
> From: Pedro Alves <palves@redhat.com>
> Date: Fri, 30 Aug 2019 13:47:06 +0100
> 
> FYI, I'm seeing these warnings with your patch:
> 
> $ make
> makeinfo --split-size=5000000  -DHAVE_MAKEINFO_CLICK -I /home/pedro/gdb/binutils-gdb/src/gdb/doc/../../readline/doc -I /home/pedro/gdb/binutils-gdb/src/gdb/doc/../mi -I /home/pedro/gdb/binutils-gdb/src/gdb/doc \
>         -o gdb.info /home/pedro/gdb/binutils-gdb/src/gdb/doc/gdb.texinfo
> /home/pedro/gdb/binutils-gdb/src/gdb/doc/gdb.texinfo:185: warning: @menu entry node name `Linux kernel @code{ptrace} restrictions' different from node name `Linux kernel ptrace restrictions'
> /home/pedro/gdb/binutils-gdb/src/gdb/doc/gdb.texinfo:44712: warning: @menu entry node name `SELinux's @code{deny_ptrace}' different from node name `SELinux's deny_ptrace'
> /home/pedro/gdb/binutils-gdb/src/gdb/doc/gdb.texinfo:44713: warning: @menu entry node name `Yama's @code{ptrace_scope}' different from node name `Yama's ptrace_scope'
> /home/pedro/gdb/binutils-gdb/src/gdb/doc/gdb.texinfo:44714: warning: @menu entry node name `Docker and @code{seccomp}' different from node name `Docker and seccomp'

We shouldn't use @-commands in node names.