Install g++

Author: electricbrass

ci/ubuntu-focal.Dockerfile

@@ -10,7 +10,7 @@ ENV TZ=US \
 # Packages - first the majority of them, then cmake
 RUN set -x && \
     apt update && \
-    apt install -y ninja-build libsdl2-dev libsdl2-mixer-dev \
+    apt install -y g++ ninja-build libsdl2-dev libsdl2-mixer-dev \
         libpng-dev libcurl4-openssl-dev libwxgtk3.0-gtk3-dev deutex \
         apt-transport-https ca-certificates gnupg software-properties-common wget && \
     wget -O - 'https://apt.kitware.com/keys/kitware-archive-latest.asc' 2>/dev/null | gpg --dearmor - | tee /etc/apt/trusted.gpg.d/kitware.gpg >/dev/null && \