Problem compiling macOS

Building on macOS Big Sur I get this error:

[ 53%] Building C object CMakeFiles/io_util_obj.dir/src/io_util/filesystem_wrapper.c.o
/Users/xxx/OpenMolcas/src/io_util/filesystem_wrapper.c:53:10: error: implicit
      declaration of function 'symlink' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  *err = symlink(to, from);
         ^
1 error generated.
make[2]: *** [CMakeFiles/io_util_obj.dir/src/io_util/filesystem_wrapper.c.o] Error 1
make[1]: *** [CMakeFiles/io_util_obj.dir/all] Error 2

If I modifying to:

void symlink_wrapper(const char* to, const char* from, INT* err)
 {
//   *err = symlink(to, from);
 }

then everything builds correctly.