style: Merge multiple consecutive RUN

Dockerfile

@@ -5,8 +5,8 @@ COPY /app/bootstrap*sh /app/
 RUN chmod +x /app/bootstrap*sh
 
 # Install OS packages required for the gem build environment.
-RUN /app/bootstrap-apt-upgrade.sh
-RUN apt-get install -y --no-install-recommends \
+RUN /app/bootstrap-apt-upgrade.sh && \
+    apt-get install -y --no-install-recommends \
       build-essential \
       cmake \
       curl \
@@ -18,8 +18,8 @@ RUN apt-get install -y --no-install-recommends \
       pkg-config \
       ruby-dev \
       shared-mime-info \
-      telnet
-RUN /app/bootstrap-apt-clean.sh
+      telnet && \
+    /app/bootstrap-apt-clean.sh
 
 # Prepare bundle for the gem build environment.
 RUN /app/bootstrap-app-dir.sh