docs: Modernise README

Refresh our README in a consistent style and update it to reflect:

* A recommendation to use binaries
* Clarify our relationship with other Rust based VMMs/Rust-VMM project
* Ensure instructions result in a usable image (cloud-init)
* Simplify script instructions
* Move compilation details elsewhere
* Add Fedora 36 image details
* Point to CLOUDHV as well as Rust Hypervisor Firmware

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

docs/building.md

@@ -0,0 +1,82 @@
+- [Building Cloud Hypervisor](#building-cloud-hypervisor)
+  - [Preparation](#preparation)
+  - [Install prerequisites](#install-prerequisites)
+  - [Clone and build](#clone-and-build)
+    - [Containerized builds and tests](#containerized-builds-and-tests)
+
+# Building Cloud Hypervisor
+
+We recommend users use the pre-built binaries that are mentioned in the README.md file in the root of the repository. Building from source is only necessary if you wish to make modifications.
+
+## Preparation
+
+We create a folder to build and run `cloud-hypervisor` at `$HOME/cloud-hypervisor`
+
+```shell
+$ export CLOUDH=$HOME/cloud-hypervisor
+$ mkdir $CLOUDH
+```
+
+## Install prerequisites
+
+You need to install some prerequisite packages in order to build and test Cloud
+Hypervisor. Here, all the steps are based on Ubuntu, for other Linux
+distributions please replace the package manager and package name.
+
+```shell
+# Install build-essential, git, and qemu-utils
+$ sudo apt install git build-essential qemu-utils
+# Install rust tool chain
+$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+# If you want to build statically linked binary please add musl target
+$ rustup target add x86_64-unknown-linux-musl
+```
+
+## Clone and build
+
+First you need to clone and build the Cloud Hypervisor repository:
+
+```shell
+$ pushd $CLOUDH
+$ git clone https://github.com/cloud-hypervisor/cloud-hypervisor.git
+$ cd cloud-hypervisor
+$ cargo build --release
+
+# We need to give the cloud-hypervisor binary the NET_ADMIN capabilities for it to set TAP interfaces up on the host.
+$ sudo setcap cap_net_admin+ep ./target/release/cloud-hypervisor
+
+# If you want to build statically linked binary
+$ cargo build --release --target=x86_64-unknown-linux-musl --all
+$ popd
+```
+
+This will build a `cloud-hypervisor` binary under
+`$CLOUDH/cloud-hypervisor/target/release/cloud-hypervisor`.
+
+### Containerized builds and tests
+
+If you want to build and test Cloud Hypervisor without having to install all the
+required dependencies (The rust toolchain, cargo tools, etc), you can also use
+Cloud Hypervisor's development script: `dev_cli.sh`. Please note that upon its
+first invocation, this script will pull a fairly large container image.
+
+For example, to build the Cloud Hypervisor release binary:
+
+```shell
+$ pushd $CLOUDH
+$ cd cloud-hypervisor
+$ ./scripts/dev_cli.sh build --release
+```
+
+With `dev_cli.sh`, one can also run the Cloud Hypervisor CI locally. This can be
+very convenient for debugging CI errors without having to fully rely on the
+Cloud Hypervisor CI infrastructure.
+
+For example, to run the Cloud Hypervisor unit tests:
+
+```shell
+$ ./scripts/dev_cli.sh tests --unit
+```
+
+Run the `./scripts/dev_cli.sh --help` command to view all the supported
+development script commands and their related options.