tools: build-image improvements

* Dockerfile fixes for podman + readability improvements
* remove unused setup script

tools/build-image/Dockerfile

 # syntax=docker/dockerfile:1
 FROM debian:stable
 ENV PATH=/root/.cargo/bin:/usr/bin:/bin
-RUN apt-get update; \
+RUN \
+    apt-get update && \
     apt-get install -y --no-install-recommends \
-        build-essential ca-certificates curl fdisk dosfstools mtools qemu-system-x86 ovmf git \
-        texlive texlive-luatex texlive-latex-extra texlive-bibtex-extra texlive-lang-german latexmk biber qpdf; \
-    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path \
-        --default-toolchain nightly --component rust-src --component miri \
-        --target x86_64-unknown-none --target x86_64-unknown-uefi; \
-    cargo miri setup; \
+        build-essential \
+        ca-certificates \
+        curl \
+        fdisk \
+        dosfstools \
+        mtools \
+        qemu-system-x86 \
+        ovmf \
+        git \
+        texlive \
+        texlive-luatex \
+        texlive-latex-extra \
+        texlive-bibtex-extra \
+        texlive-lang-german \
+        latexmk \
+        biber \
+        qpdf && \
+    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y \
+        --no-modify-path \
+        --default-toolchain nightly \
+        --component rust-src miri \
+        --target x86_64-unknown-none x86_64-unknown-uefi && \
+    cargo miri setup && \
     cargo install mdbook

tools/setup.sh

-#!/bin/sh
-
-# echo commands and fail on error
-set -ex
-
-# install dependencies
-apt-get update
-apt-get install -y --no-install-recommends \
-    build-essential ca-certificates curl fdisk dosfstools mtools qemu-system-x86 ovmf git \
-    texlive texlive-luatex texlive-latex-extra texlive-bibtex-extra texlive-lang-german latexmk biber qpdf
-
-# install rustup
-curl --proto '=https' --tlsv1.2 -sSfo rustup-init.sh https://sh.rustup.rs
-chmod +x rustup-init.sh
-./rustup-init.sh -y --default-toolchain none
-. "${HOME}/.cargo/env"
-
-# install rust toolchain
-rustup toolchain install nightly --component miri --target x86_64-unknown-none --target x86_64-unknown-uefi
-cargo miri setup
-
-# insatall mdbook
-cargo install mdbook