Use CMAKE_MSVC_RUNTIME_LIBRARY instead of LLVM_USE_CRT_*

This cmake option has been removed in:
llvm/llvm-project@618e5d2

Author: nikic

src/bootstrap/src/core/build_steps/llvm.rs

@@ -412,9 +412,7 @@ impl Step for Llvm {
         }
 
         if target.is_msvc() {
-            cfg.define("LLVM_USE_CRT_DEBUG", "MT");
-            cfg.define("LLVM_USE_CRT_RELEASE", "MT");
-            cfg.define("LLVM_USE_CRT_RELWITHDEBINFO", "MT");
+            cfg.define("CMAKE_MSVC_RUNTIME_LIBRARY", "MultiThreaded");
             cfg.static_crt(true);
         }