ci: portable retry loop in download-and-unpack for BusyBox wget

The GNU wget retry flags I added in the previous commit (--tries,
--waitretry, --timeout, --retry-connrefused) are not supported by
BusyBox wget, which is what the Alpine container image ships. Every
alpine matrix cell on run 26723340409 died immediately at the first
download with "wget: unrecognized option: waitretry=3".

Hand-roll the retry loop in bash so we only need flags that work in
both GNU and BusyBox wget (-q, -O, -U, -T). Same retry count, same
backoff, same temp-file staging — just doesn't lean on wget for the
retry semantics anymore.

Verified locally on macOS (GNU wget 1.21.3) and on
node:25-alpine3.22 (BusyBox wget) — both extract zlib's v1.3.1
tarball cleanly.

Author: JCMais

scripts/ci/download-and-unpack.sh

@@ -8,19 +8,41 @@ download_and_unpack() {
   mkdir -p "$2"
   # Download to a temp file first instead of streaming straight into tar.
   # The previous `wget -qO- | tar xzf -` pipe couldn't recover from a
-  # truncated response (e.g. curl.se/GitHub-release occasional hiccups) —
+  # truncated response (e.g. curl.se / GitHub-release occasional hiccups) —
   # tar consumes the partial bytes immediately and fails with
-  # "gzip: stdin: unexpected end of file" before wget's own retry can fire.
-  # With a temp file, wget can retry until the file is whole, and we only
+  # "gzip: stdin: unexpected end of file" before any retry can fire.
+  # With a temp file, we can retry until the file is whole, and we only
   # touch tar once.
+  #
+  # The retry loop is done in bash rather than via wget's own retry flags
+  # because Alpine ships BusyBox wget, which only supports -c/-q/-O/-U/-T —
+  # no --tries, --waitretry, --retry-connrefused. Hand-rolling the loop
+  # keeps us portable across GNU wget (Ubuntu/macOS) and BusyBox wget
+  # (Alpine container) without conditional code.
   local tmpfile
   tmpfile=$(mktemp)
   trap "rm -f \"$tmpfile\"" RETURN
+
+  local attempts=5
+  local i=1
+  local sleep_sec=3
   # User agent for Edge on macOS
-  wget --tries=5 --waitretry=3 --timeout=30 --retry-connrefused \
-       -U "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36 Edg/94.0.992.38" \
-       -qO "$tmpfile" "$1"
-  tar xzf "$tmpfile" -C "$2"
+  local user_agent="Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36 Edg/94.0.992.38"
+
+  while [ "$i" -le "$attempts" ]; do
+    # -T sets the read timeout in seconds and is available in both GNU
+    # and BusyBox wget.
+    if wget -q -T 60 -U "$user_agent" -O "$tmpfile" "$1"; then
+      tar xzf "$tmpfile" -C "$2"
+      return 0
+    fi
+    echo "download attempt $i/$attempts for $1 failed; retrying in ${sleep_sec}s..." >&2
+    i=$((i + 1))
+    sleep "$sleep_sec"
+  done
+
+  echo "download failed after $attempts attempts: $1" >&2
+  return 1
 }
 
 if [ "${1}" != "--source-only" ]; then