Some small fixes and possible valuable information #226

	name: docker cross build
	on: [push, pull_request]

	# Notes:
	#
	# - There is harmless warning:
	#
	# "[Warning] The requested image's platform (linux/arm64/v8) does not
	# match the detected host platform (linux/amd64) and no specific
	# platform was requested"
	#
	# It's hard to remove, perhaps, because we using 'build' and not 'buildx',
	# which requires more setup.
	#
	# - git clean is not necessarily on GA, but added so it's easier to copy-paste
	# Dockerfile for manual runs.

	jobs:
	cross:
	runs-on: ubuntu-22.04
	strategy:
	fail-fast: false
	matrix:
	include:
	- image: arm64v8/ubuntu:jammy
	packages: libelf-dev linux-headers-generic
	- image: arm32v7/alt:latest
	packages: elfutils kernel-headers-modules-std-def
	- image: i386/ubuntu:bionic
	packages: libelf-dev linux-headers-generic
	steps:
	- uses: docker/setup-qemu-action@v2
	- uses: actions/checkout@v3
	- name: Create Dockerfile
	run: \|
	cat <<EOF >Dockerfile
	FROM ${{ matrix.image }}
	RUN apt-get -y update && \
	apt-get install -y git file gcc make ${{ matrix.packages }}
	WORKDIR /src
	COPY . .
	RUN git clean -dxfq
	RUN gcc -v; cat /etc/os-release
	RUN make -j\$(nproc) KERNELRELEASE=\$(cd /lib/modules; ls)
	RUN file lkrg.ko
	EOF
	- run: docker build .

	# vim: sw=4

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