Multiple clang installations cannot co-exist, lets jump to the latest

Dockerfile-ubuntu2004

     apt-get -y install libssl-dev build-essential && \
     apt-get -y install vim gdb strace patch && \
     \
-    echo deb http://apt.llvm.org/focal/ llvm-toolchain-focal-10 main >> /etc/apt/sources.list && \
-    echo deb-src http://apt.llvm.org/focal/ llvm-toolchain-focal-10 main >> /etc/apt/sources.list && \
-    wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add - ; \
-    apt update -y && \
-    apt-get install -y clang-10 lldb-10 lld-10 && \
-    apt-get install -y libc++-10-dev libc++-10-dev clang-format-10 && \
-    \
-    echo deb http://apt.llvm.org/focal/ llvm-toolchain-focal-11 main >> /etc/apt/sources.list && \
-    echo deb-src http://apt.llvm.org/focal/ llvm-toolchain-focal-11 main >> /etc/apt/sources.list && \
-    wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add - ; \
-    apt update -y && \
-    apt-get install -y clang-11 lldb-11 lld-11 && \
-    apt-get install -y libc++-11-dev libc++-11-dev clang-format-11 && \
-    \
     echo deb http://apt.llvm.org/focal/ llvm-toolchain-focal-12 main >> /etc/apt/sources.list && \
     echo deb-src http://apt.llvm.org/focal/ llvm-toolchain-focal-12 main >> /etc/apt/sources.list && \
     wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add - ; \
     rm -rf cmake-3.21.3.tar.gz
 
 # Fix some weird linker issue CAF build runs into. (fails to link -lc++abi)
-RUN cp -prv /usr/lib/llvm-10/lib/libc++abi.so.1.0 /usr/lib/llvm-10/lib/libc++abi.so
-
-RUN cp -prv /usr/lib/llvm-11/lib/libc++abi.so.1.0 /usr/lib/llvm-11/lib/libc++abi.so
-
 RUN cp -prv /usr/lib/llvm-12/lib/libc++abi.so.1.0 /usr/lib/llvm-12/lib/libc++abi.so
 
 CMD "/bin/bash"