Docker: add Dockerfile for Docker container support

Dockerfile

@@ -0,0 +1,22 @@
+FROM ubuntu:16.04
+WORKDIR /ardupilot
+
+RUN useradd -U -d /ardupilot ardupilot && \
+    usermod -G users ardupilot
+
+RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install --no-install-recommends -y \
+    lsb-release \
+    sudo \
+    software-properties-common \
+    python-software-properties && \
+    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+
+ENV USER=ardupilot
+ADD . /ardupilot
+RUN chown -R ardupilot:ardupilot /ardupilot && \
+    bash -c "Tools/scripts/install-prereqs-ubuntu.sh -y && apt-get install gcc-arm-none-eabi -y" && \
+    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+
+USER ardupilot
+ENV CCACHE_MAXSIZE=1G
+ENV PATH /usr/lib/ccache:/ardupilot/Tools:${PATH}

Tools/scripts/install-prereqs-ubuntu.sh

@@ -76,7 +76,9 @@ fi
 
 sudo usermod -a -G dialout $USER
 
-$APT_GET remove modemmanager
+if dpkg-query -l "modemmanager"; then
+    $APT_GET remove modemmanager
+fi
 $APT_GET update
 
 if apt-cache search python-wxgtk3.0 | grep wx; then