Use pinnedPkgs only if initialBuild is true

src/default.nix

@@ -1,20 +1,21 @@
 # Licensed under GNU Lesser General Public License v3 or later, see COPYING.
 # Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
 
-{ arch }:
+{ arch, initialBuild ? true }:
 
 assert builtins.elem arch [ "aarch64" "i686" ];
 
 let
-  nixpkgs = import <nixpkgs> { };
+  pkgs = import <nixpkgs> { };
 
-  pinnedPkgs = import ./pinned-pkgs.nix {
+  pkgsList = import ./pkgs-list.nix {
     inherit arch;
-    inherit (nixpkgs) fetchFromGitHub;
+    inherit (pkgs) fetchFromGitHub;
   };
 in
 
 import ./pkgs {
-  inherit arch;
+  inherit arch initialBuild;
-  inherit (pinnedPkgs) buildPkgs crossPkgs crossStaticPkgs;
+  inherit (pkgsList) pinnedPkgs crossPkgs crossStaticPkgs;
+  buildPkgs = if initialBuild then pkgsList.pinnedPkgs else pkgs;
 }

src/pkgs-list.nix

@@ -5,7 +5,7 @@
 
 let
   # head of nixos-19.03 as of 2019-09-15
-  pinnedPkgs = fetchFromGitHub {
+  pinnedPkgsSrc = fetchFromGitHub {
     owner = "NixOS";
     repo = "nixpkgs";
     rev = "2dfae8e22fde5032419c3027964c406508332974";
@@ -17,10 +17,10 @@ let
     overlays = [ ];
   };
 
-  buildPkgs = import pinnedPkgs defaultNixpkgsArgs;
+  pinnedPkgs = import pinnedPkgsSrc defaultNixpkgsArgs;
 
   overlayJpegNoStatic = self: super: {
-    inherit (buildPkgs) libjpeg;
+    inherit (pinnedPkgs) libjpeg;
   };
 
   crossSystem = {
@@ -32,15 +32,15 @@ let
 in
 
 {
-  inherit buildPkgs;
+  inherit pinnedPkgs;
 
-  crossPkgs = import pinnedPkgs ({ inherit crossSystem; } // defaultNixpkgsArgs);
+  crossPkgs = import pinnedPkgsSrc ({ inherit crossSystem; } // defaultNixpkgsArgs);
 
-  crossStaticPkgs = import pinnedPkgs ({
+  crossStaticPkgs = import pinnedPkgsSrc ({
     inherit crossSystem;
 
     crossOverlays = [
-      (import "${pinnedPkgs}/pkgs/top-level/static.nix")
+      (import "${pinnedPkgsSrc}/pkgs/top-level/static.nix")
       overlayJpegNoStatic
     ];
   } // defaultNixpkgsArgs);

src/pkgs/default.nix

@@ -1,7 +1,7 @@
 # Licensed under GNU Lesser General Public License v3 or later, see COPYING.
 # Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
 
-{ arch, buildPkgs, crossPkgs, crossStaticPkgs } @ args:
+{ arch, buildPkgs, crossPkgs, crossStaticPkgs, pinnedPkgs } @ args:
 
 let
   callPackage = buildPkgs.lib.callPackageWith (args // pkgs);

src/pkgs/proot.nix

@@ -1,13 +1,13 @@
 # Licensed under GNU Lesser General Public License v3 or later, see COPYING.
 # Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
 
-{ buildPkgs, crossStaticPkgs, talloc }:
+{ pinnedPkgs, crossStaticPkgs, talloc }:
 
 crossStaticPkgs.stdenv.mkDerivation rec {
   pname = "proot-termux";
   version = "unstable-2019-09-05";
 
-  src = buildPkgs.fetchFromGitHub {
+  src = pinnedPkgs.fetchFromGitHub {
     repo = "proot";
     owner = "termux";
     rev = "3ea655b1ae40bfa2ee612d45bf1e7ad97c4559f8";

src/pkgs/talloc.nix

@@ -1,23 +1,23 @@
 # Licensed under GNU Lesser General Public License v3 or later, see COPYING.
 # Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
 
-{ buildPkgs, crossPkgs }:
+{ pinnedPkgs, crossPkgs }:
 
 crossPkgs.stdenv.mkDerivation rec {
   name = "talloc-2.1.14";
 
-  src = buildPkgs.fetchurl {
+  src = pinnedPkgs.fetchurl {
     url = "mirror://samba/talloc/${name}.tar.gz";
     sha256 = "1kk76dyav41ip7ddbbf04yfydb4jvywzi2ps0z2vla56aqkn11di";
   };
 
-  depsBuildBuild = [ buildPkgs.python2 buildPkgs.zlib ];
+  depsBuildBuild = [ pinnedPkgs.python2 pinnedPkgs.zlib ];
 
   buildDeps = [ crossPkgs.zlib ];
 
   configurePhase = ''
     substituteInPlace buildtools/bin/waf \
-      --replace "/usr/bin/env python" "${buildPkgs.python2}/bin/python"
+      --replace "/usr/bin/env python" "${pinnedPkgs.python2}/bin/python"
     ./configure --prefix=$out \
       --disable-rpath \
       --disable-python \