build: Use heredoc for Dockerfile commands (#1795)

Dockerfile

@@ -13,19 +13,25 @@ ARG DEBCONF_NOWARNINGS="yes"
 ARG DEBIAN_FRONTEND="noninteractive"
 ARG DEBCONF_NONINTERACTIVE_SEEN="true"
 
-RUN set -eu && \
-    apt-get update && \
+RUN <<EOF
+  set -eu
+
+  apt-get update
   apt-get --no-install-recommends -y install \
     samba \
     wimtools \
     dos2unix \
     cabextract \
     libxml2-utils \
-        libarchive-tools && \
-    wget "https://github.com/gershnik/wsdd-native/releases/download/v${VERSION_WSDD}/wsddn_${VERSION_WSDD}_${TARGETARCH}.deb" -O /tmp/wsddn.deb -q --timeout=10 && \
-    dpkg -i /tmp/wsddn.deb && \
-    apt-get clean && \
+    libarchive-tools
+
+  # Install wsdd
+  wget "https://github.com/gershnik/wsdd-native/releases/download/v${VERSION_WSDD}/wsddn_${VERSION_WSDD}_${TARGETARCH}.deb" -O /tmp/wsddn.deb -q --timeout=10
+  dpkg -i /tmp/wsddn.deb
+
+  apt-get clean
   rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+EOF
 
 COPY --chmod=755 ./src /run/
 COPY --chmod=755 ./assets /run/assets