debian: symlink /etc/alternatives/ from factory

Needed for several key binaries such as awk and which

Author: bluca

mkosi.conf.d/debian/mkosi.extra/usr/lib/tmpfiles.d/etc-debian.conf

@@ -8,3 +8,6 @@ L? /etc/gdm3
 
 # On Debian/Ubuntu the nftable service fails if this config is not present
 L? /etc/nftables.conf
+
+# Very basic stuff like awk and which is managed through alternatives
+L? /etc/alternatives