buildRustPackage: factor out build phase to cargoBuildHook

- API change: remove the `target` argument of `buildRustPackage`, the
  target should always be in sync with the C/C++ compiler that is used.

- Gathering of binaries has moved from `buildPhase` to `installPhase`,
  this simplifies the hook and orders this functionality logically
  with the installation logic.

pkgs/development/compilers/rust/make-rust-platform.nix

@@ -12,7 +12,7 @@ rec {
   };
 
   buildRustPackage = callPackage ../../../build-support/rust {
-    inherit rustc cargo cargoSetupHook fetchCargoTarball;
+    inherit rustc cargo cargoBuildHook cargoSetupHook fetchCargoTarball;
   };
 
   rustcSrc = callPackage ./rust-src.nix {
@@ -24,5 +24,7 @@ rec {
   };
 
   # Hooks
-  inherit (callPackage ../../../build-support/rust/hooks { }) cargoSetupHook;
+  inherit (callPackage ../../../build-support/rust/hooks {
+    inherit cargo;
+  }) cargoBuildHook cargoSetupHook;
 }