Dockerfile: use the minideb as the base image

[macbre]

Fetch non-musl binaries. This change will allow use to build multi-arch images for both x64 and aarch64.

See #28

---

$ docker images
REPOSITORY                      TAG       IMAGE ID       CREATED         SIZE
macbre/sphinx                   latest    b1577b9eaa4b   2 minutes ago   337MB
ghcr.io/macbre/sphinxsearch     latest    1cff92fe61c1   3 days ago      796MB
ghcr.io/macbre/sphinxsearch     3.8.1     c0e5be0c58bf   3 days ago      796MB

$ docker run --rm -t macbre/sphinx ldd /opt/sphinx/sphinx-3.8.1/bin/indexer
	linux-vdso.so.1 (0x00007f25214d6000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f25203e4000)
	libgomp.so.1 => /lib/x86_64-linux-gnu/libgomp.so.1 (0x00007f252039c000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f2520397000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f25202b7000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f2520297000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f25200b4000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f25214d8000)

$ docker run --rm -t ghcr.io/macbre/sphinxsearch:3.8.1 ldd /opt/sphinx/sphinx-3.8.1/bin/indexer -v
	/lib/ld-musl-x86_64.so.1 (0x7f28b4295000)
	libgomp.so.1 => /usr/lib/libgomp.so.1 (0x7f28b346a000)
	libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f28b4295000)

Sphinx 3.8.1 (commit d25e0bb3)
Copyright (c) 2001-2025, Andrew Aksyonoff
Copyright (c) 2008-2016, Sphinx Technologies Inc (http://sphinxsearch.com/)
Built on: #33~20.04.1-Ubuntu SMP Mon Feb 7 14:25:10 UTC 2022
Built with: GNU 10.5.0
Build date: May 12 2025
Build type: release
Configure flags: cmake
Compiled DB drivers: mysql-dynamic pgsql-dynamic odbc-dynamic
Compiled features: libexpat libstemmer re2 jemalloc faiss blis
Versions: binlog_format v.22, index_format v.70, udf_api v.23
Enabled dynamic drivers: mysql pgsql