fix: avoid mapfile in upload-release-to-gcs.sh

mapfile is bash 4+; macOS ships bash 3.2 at /bin/bash, so the script
errored with "mapfile: command not found" when run locally. Replace
with a portable read loop.

Author: ValentaTomas

scripts/upload-release-to-gcs.sh

@@ -73,7 +73,10 @@ echo "Release: $RELEASE_TAG (commit ${SHORT_HASH})"
 echo "Target:  ${BUCKET_URI}"
 $DRY_RUN && echo "Mode:    dry-run"
 
-mapfile -t ASSETS < <(gh release view "$RELEASE_TAG" --repo "$REPO" --json assets \
+ASSETS=()
+while IFS= read -r line; do
+  [[ -n "$line" ]] && ASSETS+=("$line")
+done < <(gh release view "$RELEASE_TAG" --repo "$REPO" --json assets \
   --jq '.assets[] | select(.name | test("^vmlinux-.*\\.bin$")) | .name')
 
 if [[ "${#ASSETS[@]}" -eq 0 ]]; then