Currently it is hard-coded to disable bmalloc and there's no way to try building. After this patch, still bmalloc is off by default and won't be compiled except passing `--no-system-malloc` option.
Committed 263399@main (7f2402e91528): <https://commits.webkit.org/263399@main> Reviewed commits have been landed. Closing PR #13170 and removing active labels.
<rdar://problem/108538763>