Custom Directory for CMake Library Output

The LIBRARY_OUTPUT_DIRECTORY target property specifies the directory where library target files will be built.

set_target_properties(JE3D PROPERTIES
         LIBRARY_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/out/library)

If all the libraries are in one directory, I find it more convenient to set the CMAKE_LIBRARY_OUTPUT_DIRECTORY variable, which is used to initialize the LIBRARY_OUTPUT_DIRECTORY property when creating a target.

set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/out/library)

Edit: Check comments if your target is a static library