remove tmp dir unconditionally at start

tools/boot/potato/boot-sparc

@@ -40,9 +40,9 @@ cp -f -p $BASEDIR/tools/boot/potato/sparc-etc/{boot-msg.txt,debian.txt,silo.conf
 	$inst/etc/
 
 tmp=/var/tmp/debian_cd
-if [ ! -d $tmp ]; then
-    mkdir -p $tmp
-fi
+rm -rf $tmp
+mkdir -p $tmp
+
 for suba in sun4cdm sun4u; do
   ln -s ../../dists/$CODENAME/main/disks-$ARCH/current/$suba/linux-a.out \
 	$inst/boot/$suba/linux