Miri CI: test aarch64-apple-darwin in PRs instead of the x86_64 target

Author: RalfJung

src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh

@@ -53,8 +53,8 @@ MIRIFLAGS="-Zmiri-force-intrinsic-fallback --cfg force_intrinsic_fallback -O -Zm
 case $HOST_TARGET in
   x86_64-unknown-linux-gnu)
     # Only this branch runs in PR CI.
-    # Fully test all main OSes, including a 32bit target.
-    python3 "$X_PY" test --stage 2 src/tools/miri src/tools/miri/cargo-miri --target x86_64-apple-darwin
+    # Fully test all main OSes, and all main architectures.
+    python3 "$X_PY" test --stage 2 src/tools/miri src/tools/miri/cargo-miri --target aarch64-apple-darwin
     python3 "$X_PY" test --stage 2 src/tools/miri src/tools/miri/cargo-miri --target i686-pc-windows-msvc
     # Only run "pass" tests for the remaining targets, which is quite a bit faster.
     python3 "$X_PY" test --stage 2 src/tools/miri --target x86_64-pc-windows-gnu --test-args pass
@@ -69,7 +69,7 @@ case $HOST_TARGET in
     #FIXME: Re-enable this once CI issues are fixed
     # See <https://github.com/rust-lang/rust/issues/127883>
     # For now, these tests are moved to `x86_64-msvc-ext2` in `src/ci/github-actions/jobs.yml`.
-    #python3 "$X_PY" test --stage 2 src/tools/miri --target aarch64-apple-darwin --test-args pass
+    #python3 "$X_PY" test --stage 2 src/tools/miri --target x86_64-apple-darwin --test-args pass
     ;;
   *)
     echo "FATAL: unexpected host $HOST_TARGET"

src/ci/github-actions/jobs.yml

@@ -522,11 +522,13 @@ auto:
   - name: x86_64-msvc-ext2
     env:
       SCRIPT: >
-        python x.py test --stage 2 src/tools/miri --target aarch64-apple-darwin --test-args pass &&
+        python x.py test --stage 2 src/tools/miri --target x86_64-apple-darwin --test-args pass &&
         python x.py test --stage 2 src/tools/miri --target x86_64-pc-windows-gnu --test-args pass &&
         python x.py miri --stage 2 library/core --test-args notest &&
         python x.py miri --stage 2 library/alloc --test-args notest &&
         python x.py miri --stage 2 library/std --test-args notest
+      # The last 3 lines smoke-test `x.py miri`. This doesn't run any actual tests (that would take
+      # too long), but it ensures that the crates build properly when tested with Miri.
       RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-msvc --enable-lld
     <<: *job-windows