download cachix with smaller closure, pin nixpkgs

.travis.yml

@@ -26,8 +26,6 @@ env:
 matrix:
   allow_failures:
     - env: GHCVERSION=ghcjs
-  exclude:
-    - env: GHCVERSION=ghc822 STRICT=false
 
 before_script:
   - sudo mount -o remount,exec,size=4G,mode=755 /run/user || true
@@ -36,8 +34,7 @@ before_script:
   - sudo launchctl kickstart -k system/org.nixos.nix-daemon || true
 
 script:
-  - nix-env -if https://github.com/cachix/cachix/tarball/master --extra-substituters https://cachix.cachix.org --trusted-public-keys 'cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-    cachix.cachix.org-1:eWNHQldwUO7G2VkjpnjDbWwy4KQ/HNxht7H4SSoMckM='
+  - nix-env -iA cachix -f https://github.com/NixOS/nixpkgs/tarball/db557aab7b690f5e0e3348459f2e4dc8fd0d9298
   - cachix use hnix
   - cachix push hnix --watch-store &
   - bash build.sh | cachix push hnix

build.sh

@@ -1,11 +1,13 @@
-#!/bin/bash -xe
+#!/usr/bin/env bash
 
+set -xe
 set -euo pipefail
 IFS=$'\n\t'
 
 GHCVERSION=${GHCVERSION:-ghc822}
 STRICT=${STRICT:-false}
 TRACING=${TRACING:-false}
+NIX_PATH=nixpkgs=https://github.com/NixOS/nixpkgs/archive/6820e2f0dd16104961d6fc7e8e38846807159c4e.tar.gz
 
 if [ "$GHCVERSION" = "ghcjs" ]; then
     nix-build --substituters 'https://nixcache.reflex-frp.org?trusted=1' ghcjs