buildroot-2022.02 installation problems

Hello
I am trying to learn Linux late, but nothing is easy.
It takes a lot of effort and time to compile individually, such as binutils, gcc, glibc, and kernel, etc which are required to build a Linux environment.
and then have discovered buildroot and i thought that the buildroot could be a little easier to reach my original purpose.
I am an engineer, so far I have developed non-linux fields such as avr, stm32f4...

I'm a beginner and I don't have an embedded board. First, I will create a virtual target using qemu on my laptop (ubuntu 20.04.3), and upload the kernel (linux-5.11.22, non-ubuntu) there. To do this, the toolchain and glibc, compiler will be created through buildroot. The first time I did it without knowing anything, it was successful, but I can't remember which option I chose.

Maybe when it first succeeded, i think the gdb option was not checked .

Afterwards, if I build with the gdb option selected for the target, an error occurs like below:
....
[Makefile:9230: all-gdb] Error 2

My current purpose is to remotely debug a virtual target program through gdbserver installed on the target based on qemu.
To do this, gdbserver must be installed on the target, but this does not work. Attached is the .config file when the error occurs.

I look forward to your reply.

host: ubuntu 20.04.3, arch: x86_64, x86_64-pc-linux-gnu-gcc
target: kernel 5.11.22(boot by qemu), arch: x86_64, x86_64-buildroot-linux-gnu-gcc
=>The command to run qemu will:
qemu-system-x86_64 -kernel /usr/src/linux-5.11.22/arch/x86/boot/bzImage -m 4096M -smp 1 -boot c -hda /home/dggil/Downloads/buildroot/output/images/rootfs.ext4 -append "root=/dev/sda rw acpi=off" -s