The ExternalProject_Add command can be used to add sources from third parties. Our first example, however, shows how to manage our own project as an assembly of different CMake projects. In this example, both the root and the leaf CMakeLists.txt declared a CMake project, that is, both of them used the project command.
ExternalProject_Add has many options that can be used to fine-tune all aspects of the configuration and compilation of external projects. These options can be classified into the following:
- Directory options: These are used to tune the structure of the source and build directories for the external project. In our case, we used the SOURCE_DIR option to let CMake know that the sources are available in the ${CMAKE_CURRENT_LIST_DIR}/src ...
