Add pipefail and comments

scripts/Dockerfile-ubuntu_21_04

@@ -3,6 +3,7 @@ FROM ubuntu:21.04 AS sunshine-ubuntu_21_04
 ARG DEBIAN_FRONTEND=noninteractive 
 ARG TZ="Europe/London"
 
+SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 RUN apt-get update -y && \
     apt-get install -y \
         build-essential \
@@ -31,7 +32,6 @@ RUN apt-get update -y && \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+# Entrypoint
 COPY build-private.sh /root/build.sh
-
-
 ENTRYPOINT ["/root/build.sh"]