set just set the variable.
Why does it not only declare but also work for add_executable?
Because I try to comment the line and the build will fail.
And EXAMPLE_SRCS_WINDOWS was only used on here. I don’t see anywhere to use it.
I haven’t looked too deeply, but based on the naming, it’s very likely that the variable EXAMPLE_SRCS_WINDOWS is used inside the function APPEND_PLATFORM_SOURCES() which is called right after the set().