ci: build cache (#1938)

* ci: build cache

* update build job

* rename steps, cache all builds, patch timestamps for ghc 8.10.7

* refactor, save O0 caches in master and stable builds

* update build to include toolchain fingerprint

* do not save cache on exact match

* remove caching docker from prs

---------

Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>

scripts/ci/prune-old-builds.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+set -eu
+
+version=$(awk '/^version:/ {print $2}' simplexmq.cabal)
+for dir in "$@"; do
+  if [ -d "$dir/build" ]; then
+    find "$dir/build" -mindepth 3 -maxdepth 3 -type d -name 'simplexmq-*' ! -name "simplexmq-$version" -exec rm -rf {} +
+  fi
+done

scripts/ci/source-timestamps.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+set -eu
+
+command=$1
+hashes=$2
+
+sources() {
+  git ls-files -z '*.hs' '*.hsc'
+}
+
+case "$command" in
+  record)
+    sources | xargs -0 sha256sum > "$hashes"
+    ;;
+  restore)
+    sources | xargs -0 touch
+    while read -r hash file; do
+      if [ -f "$file" ] && [ "$(sha256sum "$file" | cut -d' ' -f1)" = "$hash" ]; then
+        touch -d 2000-01-01 "$file"
+      fi
+    done < "$hashes"
+    ;;
+  *)
+    echo "usage: $0 record|restore <hashes file>" >&2
+    exit 1
+    ;;
+esac