Improve Microsoft/scripts/gen_modules_vhdx.sh to run without root or sudo

[julianxhokaxhiu]

Is your feature request related to a problem? Please describe.
This issue is about improving the script to generate the modules.vhdx file without requiring root. This is my own personal version but happy for everyone to contribute and improve it to every possible best practice. The script is already being used on the Arch Linux AUR package I've built ( see https://aur.archlinux.org/packages/linux-wsl2-waydroid ).

Describe the solution you'd like
See microsoft/WSL2-Linux-Kernel@0b55427 or the following code

#!/bin/bash
set -ueo pipefail

modules_dir="$1"        # e.g. "path/to/modules"
kernelver="$2"          # e.g. "6.6.114.1"
output="$3"             # e.g. "modules.vhdx"

if [ $# -ne 3 ] || [ ! -d "$modules_dir" ]; then
	printf '%s' "Usage ./$0 <modules dir> <kernelversion> <output file>" 1>&2
	exit 1
fi

if [ -e "$output" ]; then
	printf '%s' "Refusing to overwrite existing file $output" 1>&2
	exit 2
fi

# Calculate modules size (+256 MiB slack)
modules_size=$(du -bs "$modules_dir" | awk '{print $1}')
modules_size=$((modules_size + 256 * 1024 * 1024))

# ext4 block size (4 KiB)
block_size=4096
blocks=$(( (modules_size + block_size - 1) / block_size ))

# Temporary workspace
tmp_dir=$(mktemp -d)
trap 'rm -rf "$tmp_dir"' EXIT

img="$tmp_dir/modules.img"

# Create ext4 image populated from directory
mke2fs \
    -t ext4 \
    -b $block_size \
    -d "$modules_dir" \
    "$img" \
    "$blocks"

# Convert to VHDX
qemu-img convert -O vhdx "$img" "$output"

# Fix ownership since we're probably running under sudo
if [ -n "$SUDO_USER" ]; then
	chown "$SUDO_USER:$SUDO_USER" "$output"
fi

Describe alternatives you've considered
N/A

Additional context
The main idea is to improve the script to be able to run it without the need to use sudo or a root account.

[github-actions]

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How to collect WSL logs

Download and execute collect-wsl-logs.ps1 in an administrative powershell prompt:

Invoke-WebRequest -UseBasicParsing "https://raw.githubusercontent.com/microsoft/WSL/master/diagnostics/collect-wsl-logs.ps1" -OutFile collect-wsl-logs.ps1
Set-ExecutionPolicy Bypass -Scope Process -Force
.\collect-wsl-logs.ps1

The script will output the path of the log file once done.

If this is a networking issue, please use collect-networking-logs.ps1, following the instructions in Collect WSL logs for networking issues

Once completed please upload the output files to this GitHub issue.

See Collect WSL logs (recommended method).

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[julianxhokaxhiu]

/feature

[github-actions]

Diagnostic information

Found '/feature', adding tag 'feature'