Answers

1. The CMake command for creating an executable target is:

   add_executable

2. The CMake command for creating a library target is:

   add_library

3. By adding the SHARED or STATIC keyword or by setting the BUILD_SHARED_LIBS global variable
4. Object libraries are libraries that are compiled but not linked. They are useful for internally separating code and reducing compile time.
5. By globally setting the <LANG>_VISIBILITY_PRESET property
6. By calling the target_compile_options function. The compile options can be seen in the compile_commands.json file, which is generated if the CMAKE_EXPORT_COMPILE_COMMANDS variable is set to true.