Unrolled build for rust-lang#131877

Rollup merge of rust-lang#131877 - RalfJung:checktools-comment, r=ChrisDenton

checktools.sh: add link to issue for more context about disabled Miri tests

Adds some context for the changes made in rust-lang#130072.

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

@@ -59,6 +59,8 @@ case $HOST_TARGET in
     # "error: cannot produce cdylib for ... as the target ... does not support these crate types".
     # Only run "pass" tests, which is quite a bit faster.
     #FIXME: Re-enable this once CI issues are fixed
+    # See <https://github.com/rust-lang/rust/issues/127883>
+    # For now, these tests are moved to `x86_64-msvc-ext2` in `src/ci/github-actions/jobs.yml`.
     #python3 "$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 i686-pc-windows-gnu --test-args pass
     ;;

src/ci/github-actions/jobs.yml

@@ -386,6 +386,8 @@ auto:
     <<: *job-windows-8c
 
   # Temporary builder to workaround CI issues
+  # See <https://github.com/rust-lang/rust/issues/127883>
+  #FIXME: Remove this, and re-enable the same tests in `checktools.sh`, once CI issues are fixed.
   - image: x86_64-msvc-ext2
     env:
       SCRIPT: >