[docs] Update CMake cross compiling guide link

The CMake community Wiki has been moved to the [[ https://gitlab.kitware.com/cmake/community/wikis/home | Kitware GitLab Instance ]].
Also, the original anchor for `Information how to set up various cross compiling toolchains` section might not work as expected. The original content is now being collapsed, so browser won't navigate to the right section directly.

Hence, I think it might be better to provide the section name instead of `this section` with link to help readers find the right section by themselves.

Reviewed By: void

Differential Revision: https://reviews.llvm.org/D104996