should CMake add_executable include header files?

I'm pretty new to CMake, and my question is:

say we have a simple project with only

main.cpp

that uses

header.h

And i want to build this project using CMake, so i have a minimal
CMakeLists.txt that only contains the following (only what's relevant):

add_executable(MyApp main.cpp)

Is there a reason to include the header.h in the CMakeLists.txt?

From what i've seen, if i modify the header.h and run cmake again,
it update as expected.