ported double tracking from TC

docker/build/Dockerfile

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+FROM ubuntu:20.04
+
+# install the required dependencies to compile AzerothCore
+ARG DEBIAN_FRONTEND=noninteractive
+RUN apt update && apt install -y git cmake make gcc g++ clang libmysqlclient-dev libssl-dev libbz2-dev libreadline-dev libncurses-dev libace-6.4.5 libace-dev
+
+# copy the sources from the host machine to the Docker container
+ADD .git /azerothcore/.git
+ADD deps /azerothcore/deps
+ADD conf/dist /azerothcore/conf/dist
+ADD src /azerothcore/src
+ADD modules /azerothcore/modules
+ADD CMakeLists.txt /azerothcore/CMakeLists.txt
+
+ARG ENABLE_SCRIPTS=1
+ENV ENABLE_SCRIPTS=$ENABLE_SCRIPTS
+
+ENTRYPOINT  cd azerothcore/build && \
+            # run cmake
+            cmake ../ -DCMAKE_INSTALL_PREFIX=/azeroth-server -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DTOOLS=0 -DSCRIPTS=$ENABLE_SCRIPTS -DWITH_WARNINGS=1 -DCMAKE_C_FLAGS="-Werror" -DCMAKE_CXX_FLAGS="-Werror" && \
+            # calculate the optimal number of threads
+            MTHREADS=`grep -c ^processor /proc/cpuinfo`; MTHREADS=$(($MTHREADS + 2)) && \
+            # run compilation
+            make -j $MTHREADS && \
+            make install -j $MTHREADS && \
+            # copy the binary files "authserver" and "worldserver" files back to the host
+            # - the directories "/binworldserver" and "/binauthserver" are meant to be bound to the host directories
+            # - see docker/build/README.md to view the bindings
+            cp /azeroth-server/bin/worldserver /binworldserver && \
+            cp /azeroth-server/bin/authserver /binauthserver

docker/build/README.md

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+# AzerothCore Dockerized Build
+
+The AzerothCore Build Dockerfile will create a container that will run the AC build.
+
+When this container runs, it will compile AC and generate:
+
+- the build cache in the `docker/build/cache` directory
+- the `worldserver` executable file in `docker/worldserver/bin`
+- the `authserver` executable file in `docker/authserver/bin`
+
+The executable files will be used by the [authserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/authserver) and the [worldserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/worldserver) docker containers.
+
+Note: every time you update your AzerothCore sources, you **must** run again the build container and restart your `worldserver` and `authserver` containers.
+
+## Usage
+
+To build the container image you have to be in the **main** folder of your local AzerothCore sources directory and run:
+
+```
+docker build -t acbuild -f docker/build/Dockerfile .
+```
+
+Then you can launch the container to rebuild AC using:
+
+```
+docker run \
+    -v /$(pwd)/docker/build/cache:/azerothcore/build \
+    -v /$(pwd)/docker/worldserver/bin:/binworldserver \
+    -v /$(pwd)/docker/authserver/bin:/binauthserver \
+    acbuild
+```
+
+### Clearing the cache
+
+To clear the build cache, delete all files contained under the `docker/build/cache` directory.