Auto merge of rust-lang#149504 - mati865:i686-pc-windows-gnullvm, r=jieyouxu

Bring back i686-pc-windows-gnullvm target

rust-lang#148751 inadvertently removed i686-pc-windows-gnullvm std build when migrating to native CI runners. Since this change was not agreed upon, we should bring back prebuilt std builds for that target.

There are a few runners that could do it: dist-aarch64-llvm-mingw, dist-x86_64-llvm-mingw, dist-various-1 and dist-various-2.
dist-x86_64-llvm-mingw already takes slightly over 2 hours, so the faster dist-aarch64-llvm-mingw is a better choice.
We can also use dist-various-x job, they don't have llvm-mingw toolchain, but it's trivial to install one.

Author: bors

src/ci/github-actions/jobs.yml

@@ -679,15 +679,18 @@ auto:
       CODEGEN_BACKENDS: llvm,cranelift
     <<: *job-windows
 
+  # i686 has no dedicated job, build it here because this job is fast
   - name: dist-aarch64-llvm-mingw
     env:
       SCRIPT: python x.py dist bootstrap --include-default-paths
       RUST_CONFIGURE_ARGS: >-
         --build=aarch64-pc-windows-gnullvm
+        --target=aarch64-pc-windows-gnullvm,i686-pc-windows-gnullvm
         --enable-full-tools
         --enable-profiler
       DIST_REQUIRE_ALL_TOOLS: 1
       CODEGEN_BACKENDS: llvm,cranelift
+      CC_i686_pc_windows_gnullvm: i686-w64-mingw32-clang
     <<: *job-windows-aarch64
 
   - name: dist-x86_64-llvm-mingw