stdenv bootstrap tools: regenerate "officialy"

From Hydra's binaries for c5aabb0 (19.09).
This time I re-tested full stdenv bootstrap on these three platforms.
#66528 (comment)

pkgs/stdenv/linux/bootstrap-files/aarch64.nix

@@ -1,13 +1,11 @@
-# FIXME(ma27): before merging this to master we *have* to replace those files
-# as they're built for testing purposes with the aarch64 community builder.
 {
   busybox = import <nix/fetchurl.nix> {
-    url = "https://aarch64.mbosch.me/busybox";
-    sha256 = "10z8aigcj0lyfwbc4wzl7s0ng9g37sx1vsqh9sijw3hi0gfhhn4v";
+    url = http://nixos-arm.dezgeg.me/bootstrap-aarch64-2017-03-11-bb3ef8/busybox;
+    sha256 = "12qcml1l67skpjhfjwy7gr10nc86gqcwjmz9ggp7knss8gq8pv7f";
     executable = true;
   };
   bootstrapTools = import <nix/fetchurl.nix> {
-    url = "https://aarch64.mbosch.me/bootstrap-tools.tar.xz";
-    sha256 = "0n4k0l7j2yqjzicj1gyk8gdpbszqn6yj6mlx6m2pzfcm2hmbzwfk";
+    url = http://tarballs.nixos.org/stdenv-linux/aarch64/c5aabb0d603e2c1ea05f5a93b3be82437f5ebf31/bootstrap-tools.tar.xz;
+    sha256 = "d3f1bf2a1495b97f45359d5623bdb1f8eb75db43d3bf2059fc127b210f059358";
   };
 }

pkgs/stdenv/linux/bootstrap-files/i686.nix

@@ -1,12 +1,12 @@
 {
   busybox = import <nix/fetchurl.nix> {
-    url = https://lblasc-nix-dev.s3-eu-west-1.amazonaws.com/bootstrap-tools-i686-gcc9/busybox;
-    sha256 = "03g3hz2ar6nz7chfwip72gvy4wd828ha9bdgg6mjs9llsc0d2izz";
+    url = http://tarballs.nixos.org/stdenv-linux/i686/4907fc9e8d0d82b28b3c56e3a478a2882f1d700f/busybox;
+    sha256 = "ef4c1be6c7ae57e4f654efd90ae2d2e204d6769364c46469fa9ff3761195cba1";
     executable = true;
   };
 
   bootstrapTools = import <nix/fetchurl.nix> {
-    url = https://lblasc-nix-dev.s3-eu-west-1.amazonaws.com/bootstrap-tools-i686-gcc9/bootstrap-tools.tar.xz;
-    sha256 = "1m142s2z7v3v6k0m3d91prp7i71hhy394jgnkd7y3z5sh15c8j28";
+    url = http://tarballs.nixos.org/stdenv-linux/i686/c5aabb0d603e2c1ea05f5a93b3be82437f5ebf31/bootstrap-tools.tar.xz;
+    sha256 = "b9bf20315f8c5c0411679c5326084420b522046057a0850367c67d9514794f1c";
   };
 }

pkgs/stdenv/linux/bootstrap-files/x86_64.nix

@@ -3,7 +3,7 @@
 
 {
   bootstrapTools = import <nix/fetchurl.nix> {
-    url = https://lblasc-nix-dev.s3-eu-west-1.amazonaws.com/bootstrap-tools-x86-64-gcc9/bootstrap-tools.tar.xz;
-    sha256 = "0dyvaqlaszd5i2vr36h4d3k47a5xc550n1y4mkiirm1gd4ynaz1g";
+    url = http://tarballs.nixos.org/stdenv-linux/x86_64/c5aabb0d603e2c1ea05f5a93b3be82437f5ebf31/bootstrap-tools.tar.xz;
+    sha256 = "a5ce9c155ed09397614646c9717fc7cd94b1023d7b76b618d409e4fefd6e9d39";
   };
 }