make-debs.sh: clean dir to avoid build deb packages error

Without this patch, it'll hit build error in the 2nd time.
Example:
make-deb.sh  #no error: first time
make-deb.sh  #hit error: second time

Signed-off-by: Changcheng Liu <changcheng.liu@intel.com>

make-debs.sh

@@ -19,7 +19,7 @@ set -xe
 base=${1:-/tmp/release}
 codename=$(lsb_release -sc)
 releasedir=$base/$(lsb_release -si)/WORKDIR
-rm -fr $releasedir
+rm -fr $(dirname $releasedir)
 mkdir -p $releasedir
 #
 # remove all files not under git so they are not