WIP: Scratch builds

[cmeister2]

@xquery: this is just for interest - if you want me to push this forward, let me know. This generates a very small curl container which is surprisingly feature complete:

$ docker history curl/curl:7_73_0
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
...labels...
dc884e1ac7c1        8 seconds ago       /bin/sh -c #(nop) COPY file:cd6264d9a7514a8f…   231kB
0e6d4002209c        8 seconds ago       /bin/sh -c #(nop) COPY file:1baa1748c14e2a72…   3.86MB

which gives:

$ docker run -it curl/curl:7_73_0 --version
curl 7.73.0-DEV (x86_64-pc-linux-musl) libcurl/7.73.0-DEV OpenSSL/1.1.1g zlib/1.2.11 libssh2/1.9.0 nghttp2/1.40.0
Release-Date: [unreleased]
Protocols: dict file ftp ftps gopher http https imap imaps mqtt pop3 pop3s rtsp scp sftp smb smbs smtp smtps telnet tftp
Features: AsynchDNS HTTP2 HTTPS-proxy IPv6 Largefile libz NTLM NTLM_WB SSL TLS-SRP UnixSockets

[xquery]

yes I like it, though if we are to have n+1 distros we might want toreorg things a little bit.

[xquery]

closing as we are doing new work in this area, looking at https://github.com/curl/build-images for inspiration