Auto merge of rust-lang#122047 - blyxyas:llvm-ci-jemalloc, r=<try>

Use jemalloc to compile dist on CI (x86_64-linux)

Based on [this Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/Is.20the.20BOLT.20on.20CI.20using.20jemalloc/near/424424207)

I added Jemalloc for building LLVM, this should cut some CI time.

r? `@Kobzol`

Author: bors

src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile

@@ -33,6 +33,7 @@ RUN yum upgrade -y && \
       xz \
       zlib-devel.i686 \
       zlib-devel.x86_64 \
+      jemalloc-devel \
       && yum clean all
 
 RUN mkdir -p /rustroot/bin
@@ -88,7 +89,7 @@ ENV RUST_CONFIGURE_ARGS \
       --set rust.lto=thin \
       --set rust.codegen-units=1
 
-ENV SCRIPT python3 ../x.py build --set rust.debug=true opt-dist && \
+ENV SCRIPT LD_PRELOAD=`jemalloc-config --libdir`/libjemalloc.so.`jemalloc-config --revision` python3 ../x.py build --set rust.debug=true opt-dist && \
     ./build/$HOSTS/stage0-tools-bin/opt-dist linux-ci -- python3 ../x.py dist \
     --host $HOSTS --target $HOSTS \
     --include-default-paths \