hafnium: revert to use semicolon separator in the RUN command

revert https://review.trustedfirmware.org/c/ci/dockerfiles/+/6672
It was working as expected, as long as we keep "set -e" in the RUN
command.

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
Change-Id: Ifb6e0f6c3cbb781013eeaafd7d037dc528749378
diff --git a/bionic-amd64-hafnium/Dockerfile b/bionic-amd64-hafnium/Dockerfile
index c393383..c9bd057 100644
--- a/bionic-amd64-hafnium/Dockerfile
+++ b/bionic-amd64-hafnium/Dockerfile
@@ -1,7 +1,8 @@
 FROM ubuntu:18.04
 
-ENV DEBIAN_FRONTEND noninteractive
-ENV PATH=/home/buildslave/tools/bin:${PATH}
+ENV DEBIAN_FRONTEND=noninteractive
+ENV TOOLS_DIR=/home/buildslave/tools
+ENV PATH=${TOOLS_DIR}/bin:${PATH}
 ENV PKG_DEPS="\
     bc \
     bison \
@@ -30,17 +31,20 @@
 
 COPY setup-sshd /usr/sbin/setup-sshd
 
-RUN set -e \
-    && apt update -q=2 \
-    && apt install -q=2 --yes --no-install-recommends ${PKG_DEPS} \
-    && useradd -m -s /bin/bash buildslave \
-    && echo "buildslave:$BUILDSLAVE_PASSWORD" | chpasswd \
-    && echo 'buildslave ALL = NOPASSWD: ALL' > /etc/sudoers.d/jenkins \
-    && chmod 0440 /etc/sudoers.d/jenkins \
-    && mkdir -p /var/run/sshd /home/buildslave/tools \
-    && chown -R buildslave:buildslave /home/buildslave/tools \
-    && apt-get clean \
-    && rm -rf /var/lib/apt/lists/* /tmp/*
+RUN set -e ;\
+    apt update -q=2 ;\
+    apt install -q=2 --yes --no-install-recommends ${PKG_DEPS} ;\
+    # Setup buildslave user for Jenkins
+    useradd -m -s /bin/bash buildslave ;\
+    echo "buildslave:$BUILDSLAVE_PASSWORD" | chpasswd ;\
+    echo 'buildslave ALL = NOPASSWD: ALL' > /etc/sudoers.d/jenkins ;\
+    chmod 0440 /etc/sudoers.d/jenkins ;\
+    mkdir -p /var/run/sshd ${TOOLS_DIR} ;\
+    # Fix permissions
+    chown -R buildslave:buildslave ${TOOLS_DIR} ;\
+    # Cleanup
+    apt clean ;\
+    rm -rf /var/lib/apt/lists/* /tmp/*
 
 EXPOSE 22
 ENTRYPOINT ["/usr/sbin/setup-sshd"]