[alt-builder] Update to clang11

alt-builder/Dockerfile

@@ -9,9 +9,9 @@ RUN apt-get update && apt-get install -y wget gnupg && \
     apt-get update && \
     apt-get install -y g++ g++-10 g++-8 \
                        cmake ninja-build python3 \
-                       clang++-10 lld-10 libc++abi1-10 libc++abi-10-dev libc++1-10 libc++-10-dev \
-                       jq clang-tidy-10 cppcheck \
-                       clang-format-10 \
+                       clang++-11 lld-11 libc++abi1-11 libc++abi-11-dev libc++1-11 libc++-11-dev \
+                       jq clang-tidy-11 cppcheck \
+                       clang-format-11 \
                        libxml2-dev libreadline-dev qtbase5-dev graphviz-dev libjsoncpp-dev libtclap-dev \
                        libxml2 libreadline8 libqt5widgets5 graphviz libqt5xml5 libjsoncpp1 \
                        git && \
@@ -19,6 +19,7 @@ RUN apt-get update && apt-get install -y wget gnupg && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/* && \
     \
-    for file in /usr/bin/*-10; do ln -sf $file $(echo $file | sed 's/-10$//g'); done
+    for file in /usr/bin/*-10; do ln -sf $file $(echo $file | sed 's/-10$//g'); done && \
+    for file in /usr/bin/*-11; do ln -sf $file $(echo $file | sed 's/-11$//g'); done