add bullseye support

(cherry picked from commit 06c3e27fb95a46e037cf5b4542a21ff87de7e710)
(cherry picked from commit 1a0909c81d0656977e4a9c6a93a3823857038077)

Makefile

@@ -1,4 +1,4 @@
-DISTS ?= buster jessie stretch wheezy focal bionic trusty xenial
+DISTS ?= bullseye buster jessie stretch wheezy focal bionic trusty xenial
 
 VERSION ?= 5.5.0
 

create_dockerfile.sh

@@ -63,7 +63,7 @@ DATE=$(date +"%Y-%m-%d")
 
 case ${dist} in
   focal|bionic|xenial|trusty|precise) base=ubuntu ;;
-  squeeze|wheezy|jessie|stretch|buster) base=debian ;;
+  squeeze|wheezy|jessie|stretch|buster|bullseye) base=debian ;;
   *)
     echo "ERROR: no ${dist} base supported"
     exit 1