add buildkite job to run check-hydra.sh

.buildkite/pipeline.yml

@@ -25,3 +25,8 @@ steps:
       - "./check-brittany"
     agents:
       system: x86_64-linux
+
+  - label: 'release.nix'
+    command: 'scripts/buildkite/check-hydra.sh'
+    agents:
+      system: x86_64-linux

pkgs.nix

@@ -1,5 +1,5 @@
 let
-  nixpkgs = builtins.fetchTarball "https://github.com/nixos/nixpkgs/archive/38db6fdfb9672a0206a2042447132094bc05a5ea.tar.gz";
+  nixpkgs = builtins.fetchTarball "https://github.com/NixOS/nixpkgs/archive/38db6fdfb9672a0206a2042447132094bc05a5ea.tar.gz";
 in
 import nixpkgs {
   config = {

scripts/buildkite/check-hydra.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -p jq hydra -i bash -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/09195057114a0a8d112c847a9a8f52957420857d.tar.gz
+
+echo '~~~ Evaluating release.nix'
+command time --format '%e' -o eval-time.txt \
+    hydra-eval-jobs \
+    --option allowed-uris "https://github.com/NixOS https://github.com/input-output-hk" \
+    -I . release.nix > eval.json
+EVAL_EXIT_CODE="$?"
+if [ "$EVAL_EXIT_CODE" != 0 ]
+then
+  rm eval.json eval-time.txt
+  echo -e "\\e[31;1mERROR: Failed to evaluate release.nix\\e[0m"
+  exit 1
+fi
+EVAL_TIME=$(cat eval-time.txt)
+jq . < eval.json
+ERRORS=$(jq -r 'map_values(.error)|to_entries[]|select(.value)|@text "\(.key): \(.value)"' < eval.json)
+NUM_ERRORS=$(jq -r '[ map_values(.error)|to_entries[]|select(.value) ] |length' < eval.json)
+rm eval.json eval-time.txt
+
+if [ "$NUM_ERRORS" != 0 ]
+then
+  echo -e "\\e[31;1mERROR: evaluation completed in $EVAL_TIME seconds with $NUM_ERRORS errors\\e[0m"
+  echo "$ERRORS"
+  exit 1
+else
+  echo -e "\\e[32;1mOK: evaluation completed in $EVAL_TIME seconds with no errors\\e[0m"
+  exit 0
+fi