The build system for a project is generated by CMake in two phases: a configuration phase, where CMakeLists.txt is parsed, and a generation phase, where the build environment is actually generated. Generator expressions are evaluated in this second phase and can be used to tweak the build system with information that can only be known at generation time. Generator expressions are thus particularly useful when cross-compiling, where some of the information is only available after the CMakeLists.txt has been parsed, or in multi-configuration projects, where the build system is generated at once for all the different configurations the project can have, such as Debug and Release.
In our case, we will use generator expressions to ...
