util/docker/archlinux: Rename Dockerfile to Dockerfile.base

Rename Dockerfile to Dockerfile.base since additional Dockerfiles basing
on this one will be added later.

Change-Id: I70f2c89f739068749e1017524b6f8ef1b03d6456
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79344
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Zebreus <lennarteichhorn@googlemail.com>
diff --git a/util/docker/archlinux/Dockerfile b/util/docker/archlinux/Dockerfile.base
similarity index 100%
rename from util/docker/archlinux/Dockerfile
rename to util/docker/archlinux/Dockerfile.base