Is this explicit linking against OpenMP::OpenMP_CXX still necessary with this CMake linking command?

I am using CMake and GNU's parallel algorithms and the following code snippet in my CMakeLists.txt:

if (OPENMP_FOUND)    set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${OpenMP_C_FLAGS}")    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")    set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${OpenMP_EXE_LINKER_FLAGS}")endif().

Does that make the following command redundant?

target_link_libraries(MyTarget OpenMP::OpenMP_CXX)?

I have tried to find the answer here but to no avail. Upon printing the output of the above variables using the message command, I see that the last two are empty.

-- OpenMP_CXX_FLAGS are: -fopenmp-- OpenMP_C_FLAGS are: -Xclang -fopenmp -- CMAKE_EXE_LINKER_FLAGS are:  -- OpenMP_EXE_LINKER_FLAGS are:

I tried looking up the variable definition here but did not find out anything more. A small test programme using:

__gnu_parallel::for_each 

ran in parallel regardless whether I included:

target_link_libraries(MyTarget OpenMP::OpenMP_CXX) 

which leads me to conclude that it is not necessary. Is that true?

My gcc is g++-9 (Homebrew GCC 9.3.0_1) 9.3.0.

Thank you!