deps: upgrade libstdc++ to support Autodesk FBX SDK for Unity (#163)

* deps: upgrades libstdc++ to support Autodesk FBX SDK for Unity

* misc: move libstdc++ upgrade from editor to base

* misc: remove /var/lib/apt/lists in base reducing image size

images/ubuntu/base/Dockerfile

@@ -29,7 +29,8 @@ RUN apt-get -q update \
  lsb-release \
  xvfb \
  xz-utils \
- && apt-get clean
+ && apt-get clean \
+ && rm -rf /var/lib/apt/lists/*
 
 # Toolbox
 RUN apt-get -q update \
@@ -41,7 +42,18 @@ RUN apt-get -q update \
  openssh-client \
  wget \
  && git lfs install --system --skip-repo \
- && apt-get clean
+ && apt-get clean \
+ && rm -rf /var/lib/apt/lists/*
+
+# libstdc++6 upgrade
+RUN apt-get -q update \
+ && apt-get -q install -y --no-install-recommends software-properties-common \
+ && add-apt-repository -y ppa:ubuntu-toolchain-r/test \
+ && apt-get -q install -y --only-upgrade libstdc++6 \
+ && add-apt-repository -y --remove ppa:ubuntu-toolchain-r/test \ 
+ && apt-get -q remove -y --auto-remove software-properties-common \
+ && apt-get clean \
+ && rm -rf /var/lib/apt/lists/*
 
 # Disable default sound card, which removes ALSA warnings
 RUN /bin/echo -e 'pcm.!default {\n\