ci: Enable autodiff tests on x86_64 linux

src/ci/docker/host-x86_64/x86_64-gnu-autodiff/Dockerfile

@@ -0,0 +1,37 @@
+FROM ubuntu:24.04
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    g++ \
+    make \
+    ninja-build \
+    file \
+    curl \
+    ca-certificates \
+    python3 \
+    git \
+    cmake \
+    pkg-config \
+    xz-utils \
+    zlib1g-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+COPY scripts/autodiff.sh /scripts/
+
+ENV NO_DOWNLOAD_CI_LLVM 1
+ENV CODEGEN_BACKENDS llvm
+
+ENV RUST_CONFIGURE_ARGS \
+    --build=x86_64-unknown-linux-gnu \
+    --enable-llvm-enzyme \
+    --enable-llvm-link-shared \
+    --enable-ninja \
+    --enable-option-checking \
+    --disable-docs \
+    --set llvm.download-ci-llvm=false
+
+ENV SCRIPT /scripts/autodiff.sh

src/ci/docker/scripts/autodiff.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -ex
+
+../x.py build --stage 1 library
+
+../x.py test --stage 1 tests/codegen-llvm/autodiff
+../x.py test --stage 1 tests/pretty/autodiff
+../x.py test --stage 1 tests/ui/autodiff
+../x.py test --stage 1 tests/run-make/autodiff
+../x.py test --stage 1 tests/ui/feature-gates/feature-gate-autodiff.rs

src/ci/github-actions/jobs.yml

@@ -142,6 +142,8 @@ pr:
     <<: *job-linux-4c
   - name: x86_64-gnu-miri
     <<: *job-linux-4c
+  - name: x86_64-gnu-autodiff # should we move this to auto: ?
+    <<: *job-linux-4c
   - name: x86_64-gnu-gcc
     doc_url: https://rustc-dev-guide.rust-lang.org/tests/codegen-backend-tests/cg_gcc.html
     env: