Added system load limit to the CI config

.build_template_def: &build_template

    stage: build

    script:

        - export MAKEFLAGS=-j$(grep "core id" /proc/cpuinfo | wc -l)

        - export NUM_CORES=$(grep "core id" /proc/cpuinfo | wc -l)

        - export MAKEFLAGS="-l$(echo 1.5*$NUM_CORES | bc) -j$NUM_CORES"

        - mkdir -p "./builddir/$CI_JOB_NAME"

        - pushd "./builddir/$CI_JOB_NAME"

        - cmake ../..