Install clang from Ubuntu and push image from buildx

apt.llvm.org has no repository for the current ubuntu:rolling release,
and nothing pins clang 20 - CC=clang already resolved to the distro
clang. Drop the llvm.sh step along with its helper packages.

docker build now runs under the buildx docker-container driver, which
keeps the result in the build cache unless told otherwise, so push
directly from the build instead of tagging locally.

.gitea/workflows/ci.yml

@@ -35,9 +35,7 @@ jobs:
               docker push "$image:$latest"
             fi
           else
-            docker build -t "$image:$tag" -t "$image:$latest" .
-            docker push "$image:$tag"
-            docker push "$image:$latest"
+            docker build --push -t "$image:$tag" -t "$image:$latest" .
           fi
 
   pre-commit:

Dockerfile

@@ -10,20 +10,19 @@ RUN apt-get upgrade -y
 RUN TZ=America/Los_Angeles DEBIAN_FRONTEND=noninteractive apt-get install -y \
     build-essential \
     ccache \
+    clang \
     cmake \
     curl \
     devscripts \
     gcovr \
     git \
-    gnupg \
     libc6-dbg \
-    lsb-release \
+    llvm \
     mold \
     ninja-build \
     pre-commit \
     python3-requests \
     rpm \
-    software-properties-common \
     texlive-full \
     wget \
     zstd
@@ -45,11 +44,6 @@ RUN curl -Ls https://sourceware.org/pub/valgrind/valgrind-3.22.0.tar.bz2 -o valg
     cd .. && \
     rm -rf /tmp/*
 
-# Recent clang
-RUN wget https://apt.llvm.org/llvm.sh && chmod +x ./llvm.sh && ./llvm.sh 20
-
-RUN apt-get -y install clang llvm
-
 # Set after building valgrind, which doesn't build with clang for some reason
 ENV CC=clang
 ENV CXX=clang++