How to handled musl x64 becoming "official"/Tier 2

[nschonni]

No urgency or need for change, but thinking about what might need to change in this repo if nodejs/node#63737 lands.

Possible Option:

1. Do nothing, keep building here, even when the official builds start being produced
2. Turn off builds, or limit the version if the Tier 2 only starts in future releases
3. Keep serving them from this dist, but just rsync/copy the offial ones and a merged SHASUMS.txt

I don't think the musl/arm64 is on the table for Tier 2 right now, so that build would probably continue anyway.

/cc @sxa

[rvagg]

Lovely; my inclination would be to have some small period of overlap and then phase out and stop building here. Any idea if the current process of upgrading it to official would involve pushing out builds for all the active release lines or would we need to deal with older release lines here and only get official ones for the most recent line?