Prune old desktop builds from release/ on every build

build_desktop.sh now reads the version first and removes anything in
desktop/release/ that is not that version (plus the regenerated unpacked
trees), so a version bump never leaves old installers lying around — the
same rule push_desktop.sh applies to the feed.

deploy/build_desktop.sh

@@ -22,6 +22,8 @@ case "$TARGET" in
         ;;
 esac
 
+VERSION="$(node -p "require('./desktop/package.json').version")"
+
 if [ ! -d desktop/node_modules ]; then
     echo "==> Installing desktop dependencies ..."
     npm --prefix desktop ci --no-audit --no-fund
@@ -32,14 +34,25 @@ if [ "$TARGET" != "linux" ] && ! command -v wine >/dev/null 2>&1; then
     exit 1
 fi
 
+# release/ should only ever hold the current version: old installers are
+# rebuilt from git when needed, and the unpacked trees are regenerated.
+shopt -s nullglob
+stale=(desktop/release/*.deb desktop/release/*.pkg.tar.zst desktop/release/"J621 Setup "*.exe
+    desktop/release/*.blockmap desktop/release/latest*.yml)
+for file in "${stale[@]}"; do
+    case "$(basename "$file")" in
+        *"$VERSION"*) ;;
+        *) echo "    removing $(basename "$file")"; rm -f "$file" ;;
+    esac
+done
+rm -rf desktop/release/linux-unpacked desktop/release/win-unpacked
+
 case "$TARGET" in
     linux) npm --prefix desktop run dist:linux ;;
     win) npm --prefix desktop run dist:win ;;
     all) npm --prefix desktop run dist:all ;;
 esac
 
-VERSION="$(node -p "require('./desktop/package.json').version")"
-
 case "$TARGET" in
     linux) ARTIFACTS=(-name "*${VERSION}*.deb" -o -name "*${VERSION}*.pkg.tar.zst") ;;
     win) ARTIFACTS=(-name "*${VERSION}*.exe") ;;