release.nix: Add dependency on GNU Texinfo. * release.nix (tarball)[buildNativeInputs]: Add `texinfo'.
release.nix: Add dependency on GNU libgcrypt. * release.nix (build)[configureFlags]: Add `--with-libgcrypt-prefix'.
release.nix: Build out of chroot. * release.nix: Add `preConfigure' and `__noChroot' attributes.
build: Add release.nix. * release.nix: New file. * Makefile.am (EXTRA_DIST): Add it.