Release X.Y (202?-??-??)

nix repl has a new build-'n-link (:bl) command that builds a derivation while creating GC root symlinks.
The path produced by builtins.toFile is now allowed to be imported or read even with restricted evaluation. Note that this will not work with a read-only store.
nix build has a new --print-out-paths flag to print the resulting output paths. This matches the default behaviour of nix-build.
Nix can now be built with LTO by passing --enable-lto to configure. LTO is currently only supported when building with GCC.