Provide more reasoning behind -static-libgcc recommendation

[solvingj]

From the README

I would also recommend adding -static-libgcc -static-libstdc++ as well.

These flags seem to depend very much on the use case, and doesn't seem like something that can be "generally recommended" in a broad way. Can author please provide further commentary as to the reasoning this recommendation was made originally, and perhaps any known exceptions? Most importantly, is there some scenario in which using glibc_version_header absolutely requires these flags?

Related link showing how these flags have subtle but major impact on binary compatibility and should be considered carefully for each project:
Related link bazelbuild/bazel#2840