ported double tracking from TC

docker/build/Dockerfile

@@ -0,0 +1,30 @@
+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