Add 'uet cmake' command to distribute CMake-based builds over UBA

[hach-que]

This adds a uet cmake command which can be used to distribute CMake-based builds with the Unreal Build Accelerator and Kubernetes. This is mostly useful to rapidly build the Clang compiler.

Running uet cmake --help will also give you the "how to use it" information described below.

Prerequisites

Before you can distribute builds, you must configure your BuildConfiguration.xml file located at %appdata%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml with the settings to connect to the Kubernetes cluster. The Kubernetes cluster must have Windows nodes in it. You can use RKM (https://src.redpoint.games/redpointgames/rkm) to spin up a Kubernetes cluster with Windows nodes with a single command.

<?xml version="1.0" encoding="utf-8"?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
  <Kubernetes>
    <Namespace>default</Namespace>
    <Context>defafult</Context>
    <SmbServer>10.0.0.100</SmbServer>
    <SmbShare>ShareName</SmbShare>
    <SmbUsername>Domain\Username</SmbUsername>
    <SmbPassword>Password</SmbPassword>
  </Kubernetes>
</Configuration>

The 'Smb' settings specify a network share that all Windows nodes can access as the specified user. The Unreal Build Accelerator will be copied to this share and the containers will copy from this network share.

Your kubectl configuration must be connected to the cluster already, as per the 'Context' setting. You can get the context name by running kubectl config get-contexts. The 'Namespace' setting specifies what Kubernetes namespace to launch UBA agents into.

Using it

To distribute builds, you must first generate your CMake project using:

uet cmake -- ...

You should omit -G; this command will automatically select the Ninja project generator which is required to distribute builds.

Once you've generated your project, you can distribute the build using:

uet cmake -e 5.4 -- --build ...

NOTE: You must use Unreal Engine 5.4 at this time. Refer to #112 which tracks Unreal Engine 5.5 support.

The presence of --build in the CMake arguments is what this tool uses to determine whether CMake is generating project files or running the build. You only need to specify -e as an argument to this command when running the build; it is not necessary during generation.

All arguments past the -- are forwarded to CMake intact. CMake must be on your PATH or installed as part of Visual Studio 2022 Community in it's default installation location.