Revert "download llvm"

This reverts commit 7abac96.

Author: marcoieni

src/ci/github-actions/jobs.yml

@@ -435,12 +435,18 @@ auto:
     env:
       SCRIPT: make ci-mingw-x
       RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu
+      # We are intentionally allowing an old toolchain on this builder (and that's
+      # incompatible with LLVM downloads today).
+      NO_DOWNLOAD_CI_LLVM: 1
     <<: *job-windows-8c
 
   - image: x86_64-mingw-2
     env:
       SCRIPT: make ci-mingw-bootstrap
       RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu
+      # We are intentionally allowing an old toolchain on this builder (and that's
+      # incompatible with LLVM downloads today).
+      NO_DOWNLOAD_CI_LLVM: 1
     <<: *job-windows
 
   - image: dist-x86_64-msvc