ci: add lld to LLVM15 builder docker image

Author: lqd

src/ci/docker/host-x86_64/x86_64-gnu-llvm-15/Dockerfile

@@ -17,6 +17,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   gdb \
   llvm-15-tools \
   llvm-15-dev \
+  lld-15 \
   libedit-dev \
   libssl-dev \
   pkg-config \
@@ -52,3 +53,5 @@ ENV RUST_CONFIGURE_ARGS \
 COPY host-x86_64/x86_64-gnu-llvm-15/script.sh /tmp/
 
 ENV SCRIPT /tmp/script.sh
+
+ENV PATH="$PATH:/usr/lib/llvm-15/bin/"