docs: Fix instructions for building iso

Testing shows that we need changes changes:
- x86_64 cpu
- Ubuntu 22.04
- docker is required even if building without docker
- python2 instead of python
- genisoimage (for mkisofs)
- Installing Go manually (Ubuntu 22.04 have only Go 1.18)
- Target should be minikube-iso-aarch64 or minikube-iso-x86_64. Using
  arm64 and amd64 fails.

I also cleaned up a little bit the formatting to make it easier to
maintain (one package per line).

Tested building:
- minikube-iso-aarch64
- minikube-iso-x86_64

I did not test the built iso images.

Author: nirs

site/content/en/docs/contrib/building/iso.md

@@ -10,6 +10,9 @@ The minikube ISO is booted by each hypervisor to provide a stable minimal Linux
 
 ## Prerequisites
 
+* Machine with x86\_64 CPU
+* Ubuntu 22.04.5 LTS (Jammy Jellyfish)
+* docker
 * A recent GNU Make distribution (>=4.0)
 * A recent Go distribution (>=1.22.0)
 * If you are on Windows or Mac, you'll need Docker to be installed.
@@ -25,30 +28,59 @@ cd minikube
 ## Building
 
 ### Building in Docker
-To build for x86
+
+To build for x86:
+
 ```shell
 $ make buildroot-image
-$ make out/minikube-amd64.iso
+$ make minikube-iso-x86_64
 ```
 
-To build for ARM
+To build for ARM:
+
 ```shell
 $ make buildroot-image
-$ make out/minikube-arm64.iso
+$ make minikube-iso-aarch64
 ```
 
-The build will occur inside a docker container. 
+The build will occur inside a docker container.
 The bootable ISO image will be available in `out/minikube-<arch>.iso`.
 
-### Building on Baremetal
-If you want to do this on baremetal, replace `make out/minikube-<arch>.iso` with `IN_DOCKER=1 make out/minikube-<arch>.iso`.
+### Building without docker
+
+Install required tools:
+
+```shell
+sudo apt-get install \
+    automake \
+    bc \
+    build-essential \
+    cpio \
+    gcc-multilib \
+    genisoimage \
+    git \
+    gnupg2 \
+    libtool \
+    locales \
+    p7zip-full \
+    python2 \
+    unzip \
+    wget \
+```
+
+Install Go using these instructions:
+https://go.dev/doc/install
+
+To build without docker run:
 
-* Prerequisite build tools to install:
 ```shell
-sudo apt-get install build-essential gnupg2 p7zip-full git wget cpio python \
-    unzip bc gcc-multilib automake libtool locales
+IN_DOCKER=1 make minikube-iso-<arch>
 ```
 
+> [!IMPORTANT]
+> Some external projects will try to use docker even when building
+> without docker. You must install docker on the build host.
+
 ## Using a local ISO image
 
 ```shell