Set up a simple CI profiling step using nixprof

https://github.com/Kha/nixprof

.buildkite/pipeline.yml

@@ -4,6 +4,11 @@ steps:
     agents:
       system: x86_64-linux
 
+  - label: 'Run profile with ghc8107'
+    command: "./test/profile.sh ghc8107"
+    agents:
+      system: x86_64-linux
+
   - label: 'Check that jobset will evaluate in Hydra'
     command:
       - nix-build build.nix -A maintainer-scripts.check-hydra -o check-hydra.sh

test/profile.sh

@@ -0,0 +1,33 @@
+#! /usr/bin/env nix shell nixpkgs#bash nixpkgs#jq github:Kha/nixprof
+
+set -euo pipefail
+
+# check if Nix has the `ca-derivations` experimental features (code 0) is enabled
+NIX_CA_DERIVATIONS=$(jq -e '."experimental-features".value|any(. == 0)' <<< $(nix show-config --json)) || true
+NIX_BUILD_ARGS="${NIX_BUILD_ARGS:-}"
+
+cd $(dirname $0)
+
+if [ "$#" != "1" ]; then
+  echo "Please pass a compiler-nix-name to use.  For example: ./test/profile.sh ghc884"
+  exit 1
+fi
+
+GHC=$1
+
+printf "*** Cleaning package build directories..." >& 2
+rm -rvf */cabal.project.local */.ghc.environment* */dist */dist-newstyle */.stack-work
+echo >& 2
+
+printf "*** Profile the nix build...\n" >& 2
+nixprof record nix build $NIX_BUILD_ARGS \
+   -I . -I .. \
+   --option restrict-eval true \
+   --option allowed-uris "https://github.com/NixOS https://github.com/input-output-hk" \
+   --no-link --keep-going -f default.nix \
+   --argstr compiler-nix-name $GHC \
+   --arg CADerivationsEnabled $NIX_CA_DERIVATIONS
+nixprof report
+echo >& 2
+
+printf "\n*** Finished successfully\n" >& 2