* All components which won't build (yet) on Linux are excluded.
This enables switching to Linux in an application without
explicitly setting COMPONENTS to main in the main
CMakeLists.txt.
* ESP Timer provides headers for Linux now
* automatically disabling LWIP in Kconfig if it is not available
doc(linux): brought section
"Component Linux/Mock Support Overview" up to date
Now that the supported CMake version is >=3.16, this code can be
simplified.
The code to deduplicate the directories can be removed since this is
handled by target_link_directories.
