Automatic download of static curl causes certificate problems

[jamespjh]

The automatic downloading of a static curl introduced at e2501e8 can cause a problem due to lack of certificate files.

The executable downloaded has a default hardcoded certificate path at /./nix/store/6k1wq0nhs6vwxj92vdy2hz7cg1f9997p-openssl-static-x86_64-unknown-linux-musl-3.0.8-etc/etc/ssl/certs. This doesn't exist in many cases.

Can be worked around by setting CURL_CA_BUNDLE=whatever

However, I think this solution of the automatic volunteer download is too fragile, and would recommend reverting to just asking the user to set up a later curl.