travis: fix cachix support

fixes #21

.travis.yml

@@ -29,6 +29,9 @@ matrix:
 
 install:
  - nix --version
+ # for cachix we need travis to be a trusted nix user
+ - echo "trusted-users = $USER" | sudo tee -a /etc/nix/nix.conf
+ - sudo systemctl restart nix-daemon
  - if [ -n "${CACHIX_CACHE}" ]; then travis_retry nix-channel --update; fi
  - if [ -n "${CACHIX_CACHE}" ]; then nix-env -iA cachix -f https://cachix.org/api/v1/install; fi
  - if [ -n "${CACHIX_CACHE}" ]; then cachix use "${CACHIX_CACHE}"; fi