diff --git a/taskcluster/ci/toolchain/clang.yml b/taskcluster/ci/toolchain/clang.yml
index 757bdb8ea38d..13f12cca60cc 100644
--- a/taskcluster/ci/toolchain/clang.yml
+++ b/taskcluster/ci/toolchain/clang.yml
@@ -244,17 +244,15 @@ linux64-clang-13-win-cross:
         toolchain-alias: linux64-clang-win-cross
         toolchain-artifact: public/build/clang.tar.zst
     dependencies:
-        win32-compiler-rt-13: toolchain-win32-compiler-rt-13
-        win64-compiler-rt-13: toolchain-win64-compiler-rt-13
+        win64-clang-13-2stage: toolchain-win64-clang-13-2stage
     fetches:
         toolchain:
             - linux64-clang-13
-        win32-compiler-rt-13:
-            - artifact: compiler-rt.tar.zst
-              dest: x86
-        win64-compiler-rt-13:
-            - artifact: compiler-rt.tar.zst
-              dest: x86_64
+        win64-clang-13-2stage:
+            # Put this into a new directory so it doesn't conflict with the linux toolchain
+            - artifact: clang.tar.zst
+              dest: clang-cl
+              extract: false
 
 macosx64-clang-13-raw:
     description: "Clang 13 toolchain build"
diff --git a/taskcluster/ci/toolchain/compiler-rt.yml b/taskcluster/ci/toolchain/compiler-rt.yml
index a1f152651093..0fd200bad7bf 100644
--- a/taskcluster/ci/toolchain/compiler-rt.yml
+++ b/taskcluster/ci/toolchain/compiler-rt.yml
@@ -127,66 +127,6 @@ macosx64-aarch64-compiler-rt-13:
             - linux64-clang-13-stage1
             - macosx64-sdk-11.0
 
-win32-compiler-rt-13:
-    description: "win32 x86 Compiler-rt for Clang 13 toolchain build"
-    treeherder:
-        symbol: TW32(crt-13)
-    worker:
-        env:
-            TOOLTOOL_MANIFEST: "browser/config/tooltool-manifests/vs2017-15.9.manifest"
-    run:
-        arguments:
-            - i686-pc-windows-msvc
-        resources:
-            - 'taskcluster/scripts/misc/tooltool-download.sh'
-        tooltool-downloads: internal
-    fetches:
-        fetch:
-            - clang-13
-        toolchain:
-            - linux64-clang-13-stage1
-            - linux64-liblowercase
-
-win64-compiler-rt-13:
-    description: "win64 x64 Compiler-rt for Clang 13 toolchain build"
-    treeherder:
-        symbol: TW64(crt-13)
-    worker:
-        env:
-            TOOLTOOL_MANIFEST: "browser/config/tooltool-manifests/vs2017-15.9.manifest"
-    run:
-        arguments:
-            - x86_64-pc-windows-msvc
-        resources:
-            - 'taskcluster/scripts/misc/tooltool-download.sh'
-        tooltool-downloads: internal
-    fetches:
-        fetch:
-            - clang-13
-        toolchain:
-            - linux64-clang-13-stage1
-            - linux64-liblowercase
-
-win64-aarch64-compiler-rt-13:
-    description: "win64 aarch64 Compiler-rt for Clang 13 toolchain build"
-    treeherder:
-        symbol: TW64(aarch64-crt-13)
-    worker:
-        env:
-            TOOLTOOL_MANIFEST: "browser/config/tooltool-manifests/vs2017-15.9.manifest"
-    run:
-        arguments:
-            - aarch64-pc-windows-msvc
-        resources:
-            - 'taskcluster/scripts/misc/tooltool-download.sh'
-        tooltool-downloads: internal
-    fetches:
-        fetch:
-            - clang-13
-        toolchain:
-            - linux64-clang-13-stage1
-            - linux64-liblowercase
-
 wasm32-wasi-compiler-rt-13:
     description: "wasm32-wasi Compiler-rt for Clang 13 toolchain build"
     treeherder:
diff --git a/taskcluster/scripts/misc/build-compiler-rt.sh b/taskcluster/scripts/misc/build-compiler-rt.sh
index db092d2c72d8..4d5eda38bd93 100755
--- a/taskcluster/scripts/misc/build-compiler-rt.sh
+++ b/taskcluster/scripts/misc/build-compiler-rt.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-set -e -x
+set -e
 
 target=$1
 shift
@@ -107,38 +107,6 @@ aarch64-unknown-linux-gnu)
   "
   PATH="$MOZ_FETCHES_DIR/binutils/bin:$PATH"
   ;;
-*-pc-windows-msvc)
-  VSPATH="$MOZ_FETCHES_DIR/vs2017_15.9.6"
-  SDK_VERSION=10.0.17134.0
-
-  export INCLUDE="${VSPATH}/VC/include;${VSPATH}/VC/atlmfc/include;${VSPATH}/SDK/Include/${SDK_VERSION}/ucrt;${VSPATH}/SDK/Include/${SDK_VERSION}/shared;${VSPATH}/SDK/Include/${SDK_VERSION}/um"
-  case "$target" in
-  i686-pc-windows-msvc)
-    VCARCH=x86
-    ;;
-  x86_64-pc-windows-msvc)
-    VCARCH=x64
-    ;;
-  aarch64-pc-windows-msvc)
-    VCARCH=arm64
-    ;;
-  esac
-  export LIB="${VSPATH}/VC/lib/${VCARCH};${VSPATH}/VC/atlmfc/lib/${VCARCH};${VSPATH}/SDK/Lib/${SDK_VERSION}/um/${VCARCH};${VSPATH}/SDK/Lib/${SDK_VERSION}/ucrt/${VCARCH}"
-  export LD_PRELOAD=$MOZ_FETCHES_DIR/liblowercase/liblowercase.so
-  export LOWERCASE_DIRS=$VSPATH
-  clang=$MOZ_FETCHES_DIR/clang/bin/clang-cl
-  clangxx=$clang
-  ar=lib
-  EXTRA_CMAKE_FLAGS="
-    -DCMAKE_SYSTEM_NAME=Windows
-    -DCMAKE_LINKER=$MOZ_FETCHES_DIR/clang/bin/lld-link
-    -DCMAKE_MT=$MOZ_FETCHES_DIR/clang/bin/llvm-mt
-    -DCMAKE_RC_COMPILER=$MOZ_FETCHES_DIR/clang/bin/llvm-rc
-    -DCMAKE_C_FLAGS=--target=$target
-    -DCMAKE_CXX_FLAGS=--target=$target
-    -DCMAKE_ASM_FLAGS=--target=$target
-  "
-  ;;
 *)
   echo $target is not supported yet
   exit 1
@@ -160,11 +128,11 @@ eval cmake \
   $MOZ_FETCHES_DIR/llvm-project/compiler-rt \
   -GNinja \
   -DCMAKE_C_COMPILER=$clang \
-  -DCMAKE_CXX_COMPILER=${clangxx:-$clang++} \
+  -DCMAKE_CXX_COMPILER=$clang++ \
   -DCMAKE_C_COMPILER_TARGET=$target \
   -DCMAKE_CXX_COMPILER_TARGET=$target \
   -DCMAKE_ASM_COMPILER_TARGET=$target \
-  -DCMAKE_AR=$MOZ_FETCHES_DIR/clang/bin/llvm-${ar:-ar} \
+  -DCMAKE_AR=$MOZ_FETCHES_DIR/clang/bin/llvm-ar \
   -DCMAKE_RANLIB=$MOZ_FETCHES_DIR/clang/bin/llvm-ranlib \
   -DCMAKE_BUILD_TYPE=Release \
   -DLLVM_ENABLE_ASSERTIONS=OFF \
diff --git a/taskcluster/scripts/misc/repack-clang-linux-win-cross.sh b/taskcluster/scripts/misc/repack-clang-linux-win-cross.sh
index 0571f46a24d8..7f0c492c8b95 100755
--- a/taskcluster/scripts/misc/repack-clang-linux-win-cross.sh
+++ b/taskcluster/scripts/misc/repack-clang-linux-win-cross.sh
@@ -1,19 +1,15 @@
 #!/bin/bash
 set -x -e -v
 
-# This script is for building clang for windows targets on a Linux host,
-# including native Windows Compiler-RT libraries.
+# This script is to repack a linux clang with Windows clang-cl.exe and compiler runtime.
 
 cd $MOZ_FETCHES_DIR
 
-# We have a native linux64 toolchain in $MOZ_FETCHES_DIR/clang
-# We have a native x86 windows compiler-rt in $MOZ_FETCHES_DIR/x86/compiler-rt
-# We have a native x86_64 windows compiler-rt in $MOZ_FETCHES_DIR/x86_64/compiler-rt
-clang_lib=$(echo clang/lib/clang/*/lib)
-mkdir -p $clang_lib/windows
-cp x86/compiler-rt/lib/windows/* $clang_lib/windows
-cp x86_64/compiler-rt/lib/windows/* $clang_lib/windows
+# We already have the Linux clang extracted in $MOZ_FETCHES_DIR/clang by fetch-content
+# We have a non-extracted clang-cl/clang.tar.zst for Windows clang-cl that we need to extract
+# files from.
 
+$GECKO_PATH/taskcluster/scripts/misc/zstdpy -d clang-cl/clang.tar.zst | tar -x --wildcards clang/lib/clang/*/lib/windows
 tar caf clang.tar.zst clang
 
 # Put a tarball in the artifacts dir