How to disable `-rdynamic` for platforms not supporting it ?

[MichalMisiaszek]

I am trying to compile Ne10 for Xilinx bare metal ARM8 target, I updated toolchain configuration but cmake fails:
`` Linking C executable cmTC_34e2b

/tools/Xilinx/Vitis/2019.2/tps/lnx64/cmake-3.3.2/bin/cmake -E
cmake_link_script CMakeFiles/cmTC_34e2b.dir/link.txt --verbose=1

/tools/Xilinx/Vitis/2019.2/gnu/aarch64/lin/aarch64-none/bin/aarch64-none-elf-gcc
CMakeFiles/cmTC_34e2b.dir/testCCompiler.c.o -o cmTC_34e2b -rdynamic

aarch64-none-elf-gcc: error: unrecognized command line option '-rdynamic'

CMakeFiles/cmTC_34e2b.dir/build.make:97: recipe for target 'cmTC_34e2b'
failed

make[1]: *** [cmTC_34e2b] Error 1

make[1]: Leaving directory
'/home/michal/Downloads/Ne10/build/CMakeFiles/CMakeTmp'

Makefile:126: recipe for target 'cmTC_34e2b/fast' failed

make: *** [cmTC_34e2b/fast] Error 2

As this is not supported by this toolchain. How to disable it ?