Avoid overriding CMake default install prefix

CMake FetchContent is useful to incorporate subprojects at configure time. FetchContent subproject cache variables can override the top-level project cache, which can be confusing.

Projects may wish to use a default install prefix when “cmake –install-prefix” is not specified. Usually we use PROJECT_BINARY_DIR instead of CMAKE_BINARY_DIR, but in this case CMAKE_BINARY_DIR is a better choice to set the default install directory.

  # will not take effect without FORCE
  set(CMAKE_INSTALL_PREFIX ${CMAKE_BINARY_DIR} CACHE PATH "Install top-level directory" FORCE)

Another possibility is using CMakePresets.json to set the default install directory:

  "version": 3,

"configurePresets": [
  "name": "default",
  "binaryDir": "${sourceDir}/build",
  "installDir": "${sourceDir}/build"