[nix-improvements] use kaniko and manifest-tools from nixpkgs, simplify

nix/kaniko.nix

@@ -1,24 +0,0 @@
-pkgs:
-pkgs.buildGoModule rec {
-  pname = "kaniko";
-  version = "1.9.2";
-
-  src = pkgs.fetchFromGitHub {
-    owner = "GoogleContainerTools";
-    repo = "kaniko";
-    rev = "v${version}";
-    sha256 = "dXQ0/o1qISv+sjNVIpfF85bkbM9sGOGwqVbWZpMWfMY=";
-  };
-
-  vendorSha256 = null;
-
-  checkPhase = "true";
-
-  meta = with pkgs.lib; {
-    description =
-      "kaniko is a tool to build container images from a Dockerfile, inside a container or Kubernetes cluster.";
-    homepage = "https://github.com/GoogleContainerTools/kaniko";
-    license = licenses.asl20;
-    platforms = platforms.linux;
-  };
-}

nix/manifest-tool.nix

@@ -1,24 +0,0 @@
-pkgs:
-pkgs.buildGoModule rec {
-  pname = "manifest-tool";
-  version = "2.0.5";
-
-  src = pkgs.fetchFromGitHub {
-    owner = "estesp";
-    repo = "manifest-tool";
-    rev = "v${version}";
-    sha256 = "hjCGKnE0yrlnF/VIzOwcDzmQX3Wft+21KCny/opqdLg=";
-  } + "/v2";
-
-  vendorSha256 = null;
-
-  checkPhase = "true";
-
-  meta = with pkgs.lib; {
-    description =
-      "Command line tool to create and query container image manifest list/indexes";
-    homepage = "https://github.com/estesp/manifest-tool";
-    license = licenses.asl20;
-    platforms = platforms.linux;
-  };
-}

nix/toolchain.nix

@@ -1,11 +0,0 @@
-{ system ? builtins.currentSystem, }:
-
-with import ./common.nix;
-
-let
-  pkgsHost = import pkgsSrc { };
-  kaniko = (import ./kaniko.nix) pkgsHost;
-  winscp = (import ./winscp.nix) pkgsHost;
-  manifestTool = (import ./manifest-tool.nix) pkgsHost;
-in [ kaniko winscp manifestTool ]
-