KASM-3184 force the use of gcc11

builder/dockerfile.kali_kali-rolling.build

@@ -4,6 +4,8 @@ ENV KASMVNC_BUILD_OS kali
 ENV KASMVNC_BUILD_OS_CODENAME kali-rolling
 ENV XORG_VER 1.20.10
 ENV DEBIAN_FRONTEND noninteractive
+ENV CC=gcc-11
+ENV CXX=g++-11
 
 RUN grep '^deb'  /etc/apt/sources.list | sed 's#^deb#deb-src#' >> /etc/apt/sources.list
 
@@ -12,6 +14,7 @@ RUN apt-get update && \
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends tzdata
 RUN apt-get update && apt-get -y build-dep xorg-server libxfont-dev
+RUN apt-get update && apt-get -y install gcc-11 g++-11
 RUN apt-get update && apt-get -y install cmake git libjpeg-dev libgnutls28-dev vim wget tightvncserver
 RUN apt-get update && apt-get -y install libpng-dev libtiff-dev libgif-dev libavcodec-dev libssl-dev libxrandr-dev libxcursor-dev
 
@@ -20,7 +23,7 @@ RUN cd /tmp && wget https://storage.googleapis.com/downloads.webmproject.org/rel
 RUN cd /tmp && tar -xzf /tmp/libwebp-*
 RUN cd /tmp/libwebp-1.0.2 && \
     ./configure --enable-static --disable-shared && \
-    make && make install
+    make -j$(nproc) && make install
 
 RUN useradd -m docker && echo "docker:docker" | chpasswd && adduser docker sudo