diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f1c87b0a76e15..986122ffb30d7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -52,19 +52,13 @@ jobs:
     strategy:
       matrix:
         include:
-          - name: mingw-check
-            os: ubuntu-20.04-4core-16gb
-            env: {}
-          - name: mingw-check-tidy
-            os: ubuntu-20.04-4core-16gb
-            env: {}
-          - name: x86_64-gnu-llvm-17
+          - name: i686-mingw
             env:
-              ENABLE_GCC_CODEGEN: "1"
-            os: ubuntu-20.04-16core-64gb
-          - name: x86_64-gnu-tools
-            os: ubuntu-20.04-16core-64gb
-            env: {}
+              RUST_CONFIGURE_ARGS: "--build=i686-pc-windows-gnu"
+              SCRIPT: make ci-mingw
+              NO_DOWNLOAD_CI_LLVM: 1
+              CUSTOM_MINGW: 1
+            os: windows-2019-8core-32gb
     defaults:
       run:
         shell: "${{ contains(matrix.os, 'windows') && 'msys2 {0}' || 'bash' }}"
diff --git a/Cargo.lock b/Cargo.lock
index d5c9a5e4d0d0e..ba12997247786 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -741,8 +741,7 @@ checksum = "55b672471b4e9f9e95499ea597ff64941a309b2cdbffcc46f2cc5e2d971fd335"
 [[package]]
 name = "compiler_builtins"
 version = "0.1.108"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d68bc55329711cd719c2687bb147bc06211b0521f97ef398280108ccb23227e9"
+source = "git+https://github.com/rust-lang/compiler-builtins?branch=master#d8ab794ed61e2c7c0750f57332a680d5aa8db48c"
 dependencies = [
  "cc",
  "rustc-std-workspace-core",
diff --git a/Cargo.toml b/Cargo.toml
index e12c968e205b7..1a5376e4db3bd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -111,6 +111,7 @@ strip = true
 rustc-std-workspace-core = { path = 'library/rustc-std-workspace-core' }
 rustc-std-workspace-alloc = { path = 'library/rustc-std-workspace-alloc' }
 rustc-std-workspace-std = { path = 'library/rustc-std-workspace-std' }
+compiler_builtins = { git = "https://github.com/rust-lang/compiler-builtins", branch = "master" }
 
 [patch."https://github.com/rust-lang/rust-clippy"]
 clippy_lints = { path = "src/tools/clippy/clippy_lints" }
diff --git a/src/ci/github-actions/ci.yml b/src/ci/github-actions/ci.yml
index 80e2357440432..c48882c2002dc 100644
--- a/src/ci/github-actions/ci.yml
+++ b/src/ci/github-actions/ci.yml
@@ -351,19 +351,15 @@ jobs:
     strategy:
       matrix:
         include:
-          - name: mingw-check
-            <<: *job-linux-4c
-
-          - name: mingw-check-tidy
-            <<: *job-linux-4c
-
-          - name: x86_64-gnu-llvm-17
+          - name: i686-mingw
             env:
-              ENABLE_GCC_CODEGEN: "1"
-            <<: *job-linux-16c
-
-          - name: x86_64-gnu-tools
-            <<: *job-linux-16c
+              RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu
+              SCRIPT: make ci-mingw
+              # We are intentionally allowing an old toolchain on this builder (and that's
+              # incompatible with LLVM downloads today).
+              NO_DOWNLOAD_CI_LLVM: 1
+              CUSTOM_MINGW: 1
+            <<: *job-windows-8c
 
   auto:
     <<: *base-ci-job
diff --git a/src/tools/tidy/src/extdeps.rs b/src/tools/tidy/src/extdeps.rs
index ff71ca537256f..3e3249c67520e 100644
--- a/src/tools/tidy/src/extdeps.rs
+++ b/src/tools/tidy/src/extdeps.rs
@@ -4,7 +4,10 @@ use std::fs;
 use std::path::Path;
 
 /// List of allowed sources for packages.
-const ALLOWED_SOURCES: &[&str] = &["\"registry+https://github.com/rust-lang/crates.io-index\""];
+const ALLOWED_SOURCES: &[&str] = &[
+    "\"registry+https://github.com/rust-lang/crates.io-index\"",
+    "\"git+https://github.com/rust-lang/compiler-builtins?branch=master#d8ab794ed61e2c7c0750f57332a680d5aa8db48c\"",
+];
 
 /// Checks for external package sources. `root` is the path to the directory that contains the
 /// workspace `Cargo.toml`.