When you compile GCC you need to provide a full glibc installation as your target. It is also a dependency of libstdc++.

C++ global/static variable initialization depends on the specific version of glibc (they don't usually break compat, but they can and they did in the past) which also provides ld-linux.so that loads those global variable placeholders in the correct manner such that glibc and libstdc++ can initialize them correctly.

This is just one example. Thread local variables and behavior of things like pthreads with signal, fork etc all depend on glibc.