Index: cmake/modules/LLVMExternalProjectUtils.cmake
===================================================================
--- cmake/modules/LLVMExternalProjectUtils.cmake
+++ cmake/modules/LLVMExternalProjectUtils.cmake
@@ -106,8 +106,13 @@

   if(ARG_USE_TOOLCHAIN AND NOT CMAKE_CROSSCOMPILING)
     if(CLANG_IN_TOOLCHAIN)
-      set(compiler_args -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
-                        -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++)
+      if(${${nameCanon}_CMAKE_SYSTEM_NAME} STREQUAL Windows)
+        set(compiler_args -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang-cl
+                          -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang-cl)
+      else()
+        set(compiler_args -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
+                          -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++)
+      endif()
     endif()
     if(lld IN_LIST TOOLCHAIN_TOOLS)
       list(APPEND compiler_args -DCMAKE_LINKER=${LLVM_RUNTIME_OUTPUT_INTDIR}/ld.lld)