Description of the Core Build System.

A brief explanation of what the Core Build System is for end users.

doc/org.eclipse.cdt.doc.user/src/asciidoc/core_build_system.adoc

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+////
+Copyright (c) 2000-2024 QNX Software Systems and others
+This program and the accompanying materials
+are made available under the terms of the Eclipse Public License 2.0
+which accompanies this distribution, and is available at
+https://www.eclipse.org/legal/epl-2.0/
+
+SPDX-License-Identifier: EPL-2.0
+////
+
+
+// support image rendering and table of contents within GitHub
+ifdef::env-github[]
+:imagesdir: ../../images
+:toc:
+:toc-placement!:
+endif::[]
+
+// enable support for button, menu and keyboard macros
+:experimental:
+
+= Core Build System
+
+The Core Build System is the successor of the Managed Build System.
+
+The classical Makefile projects are based on the Managed Build System.
+Managed Build projects can generate a Makefile based on GUI controlled
+build configurations in the project properties. The user can
+manage the separate build configurations for Run and Debug. There is a
+notion of "active" build configuration, which is the one that gets
+built when the build button is pressed.
+
+The Core Build System is the basis for CMake projects and Core Build
+Makefile projects. The CDT LaunchBar plays a central role and is used
+for building and launching the program. The philosophy is "Build for
+launch". It simplified the flow a lot.
+
+These are the main differences with the old Managed Build System:
+
+* No build configurations. No build file (Makefile or
+  CMakeLists.txt) generation. The user writes it by hand. A
+  "helloworld" example build file can be created for new projects.
+* A project gets immediately a launch configuration tied to it.
+* Build settings are in the launch configuration Build Settings tab.
+* The LaunchBar determines Run or Debug mode for building. There is no
+  more concept of an active build configuration like in the Managed
+  Build projects.
+* Auto discovery. The project's macro definitions and include paths,
+  needed for indexing, are extracted from the build step. For CMake
+  projects this is done via the generated JSON file. For Makefile
+  projects it is extracted from the build step console output.
+* Using existing code is simply done by creating a new project on top
+  of the existing code. No more project import.
+
+Thanks to the auto discovery the indexing of the C/C++ code has
+improved, because all compilation flags are known per file. Especially
+for projects that use multiple toolchains in one project.