Add GCC to container

Required for b2 bootstrap

Author: Flamefire

.github/workflows/unit-tests.yml

@@ -133,12 +133,16 @@ jobs:
             find "$BOOST_ROOT"/lib/cmake -type f
             echo "BOOST_ROOT=${BOOST_ROOT}" >> $GITHUB_ENV
           else
+            echo "DEBIAN_FRONTEND=noninteractive" >> $GITHUB_ENV
+            export DEBIAN_FRONTEND=noninteractive
+
             if [ -n "${{matrix.container}}" ] && [ -f "/etc/debian_version" ]; then
               apt-get -o Acquire::Retries=5 update
               apt-get -o Acquire::Retries=5 -y -q --no-install-suggests --no-install-recommends install \
                 sudo \
                 software-properties-common \
                 bzip2 \
+                g++ \
                 git \
                 make \
                 wget