buildVimPlugin: enable structuredAttrs

it's a cool feature, let's enable it before release to find issues early

the neovimRequireCheckHook needed changes since now 'dependencies' is
seen as a bash array instead of a string:
1. we first expand it as a string
2. we replace ' ' with ',' (as before)

pkgs/applications/editors/vim/plugins/build-vim-plugin.nix

@@ -24,6 +24,7 @@
       drv = stdenv.mkDerivation (attrs // {
         name = lib.warnIf (attrs ? vimprefix) "The 'vimprefix' is now hardcoded in toVimPlugin" name;
 
+        __structuredAttrs = true;
         inherit unpackPhase configurePhase buildPhase addonInfo preInstall postInstall;
 
         installPhase = ''

pkgs/applications/editors/vim/plugins/neovim-require-check-hook.sh

@@ -1,3 +1,4 @@
+#shellcheck shell=bash
 # Setup hook for checking whether Python imports succeed
 echo "Sourcing neovim-require-check-hook.sh"
 
@@ -9,8 +10,10 @@ neovimRequireCheckHook () {
 
 		# editorconfig-checker-disable
         export HOME="$TMPDIR"
+
+        local deps="${dependencies[*]}"
         @nvimBinary@ -es --headless -n -u NONE -i NONE --clean -V1 \
-            --cmd "set rtp+=$out,${dependencies// /,}" \
+            --cmd "set rtp+=$out,${deps// /,}" \
             --cmd "lua require('$nvimRequireCheck')"
     fi
 }