Copy target file to another location in a post build step in CMake

Use generator expressions in the POST_BUILD command instead of manually computing the output path. These are configuration aware. Example:

add_custom_command(TARGET mylibrary POST_BUILD 
  COMMAND "${CMAKE_COMMAND}" -E copy 
     "$<TARGET_FILE:mylibrary>"
     "my_target_path/$<CONFIGURATION>/$<TARGET_FILE_NAME:mylibrary>" 
  COMMENT "Copying to output directory")

Rather than using the obsolete LOCATION property, prefer using generator expressions:

add_custom_command(TARGET mylibrary POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_FILE:mylibrary> ${targetfile}
)

You could also just generate the exe in the target directory directly by setting the target property RUNTIME_OUTPUT_DIRECTORY instead of copying it. This has per-configuration options (e.g. RUNTIME_OUTPUT_DIRECTORY_DEBUG).

set_target_properties(mylibrary PROPERTIES
                      RUNTIME_OUTPUT_DIRECTORY_DEBUG <debug path>
                      RUNTIME_OUTPUT_DIRECTORY_RELEASE <release path>
)

For further details run:

cmake --help-property "RUNTIME_OUTPUT_DIRECTORY"
cmake --help-property "RUNTIME_OUTPUT_DIRECTORY_<CONFIG>"

Also, you should be able to use forward slashes throughout for path separators, even on Windows.

The other answers weren't 100% clear to me...

Say you're building an executable test_base.exe, the following will build the executable then copy the .exe to the base 'build' directory:

add_executable(test_base "")
target_sources(test_base
    PRIVATE
        catch_main.cpp
        catch_tests.cpp
        sc_main.cpp
)
target_link_libraries(test_base PRIVATE Catch2 systemc)

add_custom_command(TARGET test_base POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_FILE:test_base> ${PROJECT_BINARY_DIR}/test_base.exe
    COMMENT "Created ${PROJECT_BINARY_DIR}/test_base.exe"
)

So, after this runs your project will have:

<project dir>/build/test_base.exe