Motivation for this change

On current master, running nix-build . -A adoptopenjdk-hotspot-bin-8 results in ln: failed to create symbolic link '/nix/store/fkhmgiyh6sh65x0x27wwlsz1m2nv5wrw-adoptopenjdk-hotspot-bin-8.0.222/jre': File exists.

Things done

I make sure that this backwards compatability mechanism isn't breaking builds on older jdk versions, by checking first if the directory exists (and hence the need for this ln -s call).

• [ x ] Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • [ x ] macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• [ x ] Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

Notify maintainers

cc @taku0