Can one add further source files to an executable once defined?

Question

Given I have defined an executable with its main source file in a CMakeList.txt file:

ADD_EXECUTABLE(MyExampleApp main.cpp)

Can I

Answer 1

I think you may use:

add_executable(MyExampleApp main.cpp)
add_library(library STATIC ${ADDITIONAL_SOURCES})
set_target_properties(library PROPERTIES
     LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
target_link_libraries(MyExampleApp library)