Some developers would be happier with the gtest version provided from
their package manager. Use it if it is installed the package provide
cmake support.
Fixed: https://github.com/ArthurSonzogni/FTXUI/issues/551
The target_compile_features command allows setting PUBLIC compile features for the library, making it implicit for the applications linking it. This reduces the CMake boilerplate required to set up a dependent project (eg. ftxui-starter).
