[Bug] Kernel Config for building x86 5.10 fails

[wimax-grapl]

Describe the bug

I tried following these instructions to build a microVM kernel, but for the other extant x86 config, 5.10.

To Reproduce

wimax@penguin:/tmp/tmp.fnIrRQe1JO/firecracker$ git log | head -n5
commit d3e98b9a4ae024de63f072c57015d8b7b0c1b061
Author: Luminita Voicu <[email protected]>
Date:   Fri Jan 28 14:20:05 2022 +0200

    release v1.0


wimax@penguin:/tmp/tmp.fnIrRQe1JO/firecracker$ readonly KERNEL="x86_64-5.10"
wimax@penguin:/tmp/tmp.fnIrRQe1JO/firecracker$ readonly KERNEL_CONFIG="resources/guest_configs/microvm-kernel-${KERNEL}.config"


wimax@penguin:/tmp/tmp.fnIrRQe1JO/firecracker$ ./tools/devtool build_kernel --config "${KERNEL_CONFIG}" --nproc 8
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  6046  100  6046    0     0  38509      0 --:--:-- --:--:-- --:--:-- 38509
Starting kernel build.
Downloading kernel from https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.0.tar.xz
Extracting kernel sources...
tar: This does not look like a tar archive
xz: (stdin): File format not recognized
tar: Child returned status 1
tar: Error is not recoverable: exiting now
cp: cannot create regular file '/tmp/tmp.fnIrRQe1JO/firecracker/build/kernel/linux-5.10.0/.config': No such file or directory
[ERROR] Kernel directory not found.

[Firecracker devtool] Successfully built kernel!
[Firecracker devtool] Kernel binary placed in: /tmp/tmp.fnIrRQe1JO/firecracker/build/kernel/linux-5.10.0/vmlinux-5.10.0-x86_64.bin
wimax@penguin:/tmp/tmp.fnIrRQe1JO/firecracker$ ls /tmp/tmp.fnIrRQe1JO/firecracker/build/kernel/linux-5.10.0/vmlinux-5.10.0-x86_64.bin
ls: cannot access '/tmp/tmp.fnIrRQe1JO/firecracker/build/kernel/linux-5.10.0/vmlinux-5.10.0-x86_64.bin': No such file or directory

Expected behaviour

1. I would have expected a kernel to be built. It looks like 5.10.0 does not exist on https://cdn.kernel.org/pub/linux/kernel/v5.x/ for starters!
2. Moreover, I would have expected Devtool to not give me these clearly incorrect "Successfully built kernel!" messages intermixed with the failures.

Environment

[Author TODO: Please supply the following information):] [ - Firecracker version.] 1.0.0 [ - Host and guest kernel versions.] Host: Debian Bullseye on Crostini: 5.4.163-17383-gbc0d0d65633b [ - Rootfs used.] [ - Architecture.] [ - Any other relevant software versions.]

Additional context

Checks

• [x] Have you searched the Firecracker Issues database for similar problems?
• [x] Have you read the existing relevant Firecracker documentation?
• [x] Are you certain the bug being reported is a Firecracker issue?