Update Dockerfile-prebuilt

Dockerfile-prebuilt

 FROM ubuntu:focal as decker
 
-RUN apt-get update && apt-get install -y \
-    graphviz \
-    gnuplot \
-    rsync \
-    unzip \
-    zip
-
-COPY decker /usr/bin/decker 
-
 #set the encoding on UTF-8, so the parser works correctly, german language is also added for umlaute
 #source of fix: https://blog.mkowalski.net/2016/05/16/solving-locale-issues-with-docker-containers/
-RUN apt-get install --reinstall -y locales && \
+RUN apt-get update && apt-get install --reinstall -y locales && \
     sed -i 's/# de_DE.UTF-8 UTF-8/de_DE.UTF-8 UTF-8/' /etc/locale.gen && \
     locale-gen de_DE.UTF-8
 ENV LANG de_DE.UTF-8
@@ -19,6 +10,18 @@ ENV LANGUAGE de_DE
 ENV LC_ALL de_DE.UTF-8
 RUN dpkg-reconfigure --frontend noninteractive locales
 
+ENV DEBIAN_FRONTEND noninteractive
+RUN apt-get -y install tzdata
+
+RUN apt-get install -y \
+    graphviz \
+    gnuplot \
+    rsync \
+    unzip \
+    zip
+
+COPY decker /usr/bin/decker 
+
 WORKDIR /decker
 
 ENTRYPOINT ["decker"]