add config.environment.ld-linux

Add option to install symlink to ld-linux(8) system-wide to allow running unmodified ELF binaries.
It might be useful to run games or executables distributed inside jar files as discussed
https://discourse.nixos.org/t/runtime-alternative-to-patchelf-set-interpreter/3539
https://discourse.nixos.org/t/running-binaries-without-fhs-and-patchelf/1828

It is the third concession to FHS after `/bin/sh` and `/usr/bin/env` but it is disabled by default unlike those two