fzf: fix invalid symlink on vim-plugins
fzf: fix invalid symlink on vim-plugins

The fzf vim plugin wasn't working because it was making a symlink to a
directory with the full source code. This directory isn't present
anymore since the commit e95f17e2720e67e2eabd59d7754c814d3e27a0b2 wich
removes it because it isn't so useful for the go packages.

I fixed it by manually copying the plugin/ directory into the out
derivation, which is the only part of the source that contains the vim
plugin.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs