donot make executable after catkin_make

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My operating system is ubuntu20.04, and the ros version is noetic.

I downloaded a package on the Internet, and catkin_make did not show an error, but I found that it did not generate an executable when I ran it.

I make sure that my cmakelist is in the following order of declaration:

find_package()

catkin_package()

include_directories()

add_executable()

target_link_libraries()

I have two files, infantry2020_node1.cpp and infantry2020_node1.h. I hope they can be compiled into an executable called emulator_node. My catkin_make shows no errors, but I can't find the corresponding executable in devel. By the way, there is a corresponding package folder in my /devel/lib/, but there is no executable in there. Moreover, this package can be run on my brother's computer. His system and ros version are the same as mine.I am so confused! Can anyboy help me？ Thanks so much!