Several cross toolchains mirrored from musl.cc
musl.cc gets effectively DDOSed by Microsoft's CI: https://github.com/orgs/community/discussions/27906#discussioncomment-3332440 So the IP ranges are blocked.
Here we have a copy of cross toolchains for our workflows. Toolchains are uploaded as part of releases: https://github.com/rizinorg/cross-toolchains/releases