tools/direnv: fix direnv+flycheck integration
tools/direnv: fix direnv+flycheck integration

Also fixes direnv+flycheck for nix users by consulting direnv before
looking for flycheck executables.

UndeadKernel/emacs_doom,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,UndeadKernel/emacs_doom,hlissner/.emacs.d,UndeadKernel/emacs_doom,hlissner/doom-emacs,hlissner/.emacs.d,UndeadKernel/emacs_doom,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,UndeadKernel/emacs_doom,UndeadKernel/emacs_doom,hlissner/doom-emacs,hlissner/.emacs.d,UndeadKernel/emacs_doom,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs