mkosi: Prevent busybox from getting pulled into opensuse images

OpenSUSE's busybox has a bunch of Provides for basic tools that cause
it to get pulled into images unless the corresponding tool is explicitly
installed so let's add explicit tools to make sure we don't get busybox.

(cherry picked from commit 857e452)

Author: DaanDeMeyer

mkosi.images/base/mkosi.conf.d/10-opensuse.conf

@@ -8,6 +8,7 @@ Distribution=opensuse
 # versions don't get installed instead.
 Packages=
         device-mapper
+        diffutils
         distribution-release
         docbook-xsl-stylesheets
         gawk