cargoDocsetHook: invoke via cargo

this makes sure we really have all the dependencies on the PATH which we need

pkgs/additional/cargo-docset/hook.nix

@@ -1,9 +1,10 @@
 { makeSetupHook
+, cargo
 , cargoDocset
 }:
 makeSetupHook {
   name = "cargo-docset-hook";
   propagatedBuildInputs = [
-    cargoDocset
+    cargo cargoDocset
   ];
 } ./hook.sh

pkgs/additional/cargo-docset/hook.sh

@@ -2,7 +2,7 @@ postBuildHooks+=(_cargoDocset)
 postInstallHooks+=(_cargoDocsetInstall)
 
 _cargoDocset() {
-  cargo-docset docset
+  cargo docset
 }
 
 _cargoDocsetInstall() {