Add clang-11

Author: saethlin

src/ci/docker/host-x86_64/pr-check-2/Dockerfile

@@ -2,6 +2,7 @@ FROM ubuntu:22.04
 
 ARG DEBIAN_FRONTEND=noninteractive
 RUN apt-get update && apt-get install -y --no-install-recommends \
+  clang-11 \
   g++ \
   make \
   ninja-build \