Support --sysroot= for ${arch}-windows-msvc targets

I think it is possible to use the same rule for msvc targets with
--target= and --sysroot=

See Repository:
https://github.com/trcrsired/windows-msvc-sysroot

Add sysroot support for msvc

MSVC.cpp needs getDriver before using D

add stl in parser for -stdlib=

Add Vcruntime to runtime list and unwind list

MSVC add default runtime lib type and default unwind lib type

add a msvc sysroot test

use %S instead of /foo

Fix test for msvc-sysroot

Also add a pesudo implementation for WebAssembly and
maybe Microsoft STL could be ported to more targets in the future

clang/include/clang/Driver/ToolChain.h

@@ -95,18 +95,21 @@ class ToolChain {
 
   enum CXXStdlibType {
     CST_Libcxx,
-    CST_Libstdcxx
+    CST_Libstdcxx,
+    CST_Stl,
   };
 
   enum RuntimeLibType {
     RLT_CompilerRT,
-    RLT_Libgcc
+    RLT_Libgcc,
+    RLT_Vcruntime
   };
 
   enum UnwindLibType {
     UNW_None,
     UNW_CompilerRT,
-    UNW_Libgcc
+    UNW_Libgcc,
+    UNW_Vcruntime
   };
 
   enum class UnwindTableLevel {

clang/lib/Driver/ToolChain.cpp

@@ -1091,6 +1091,8 @@ ToolChain::RuntimeLibType ToolChain::GetRuntimeLibType(
     runtimeLibType = ToolChain::RLT_CompilerRT;
   else if (LibName == "libgcc")
     runtimeLibType = ToolChain::RLT_Libgcc;
+  else if (LibName == "vcruntime")
+    runtimeLibType = ToolChain::RLT_Vcruntime;
   else if (LibName == "platform")
     runtimeLibType = GetDefaultRuntimeLibType();
   else {
@@ -1129,6 +1131,8 @@ ToolChain::UnwindLibType ToolChain::GetUnwindLibType(
     unwindLibType = ToolChain::UNW_CompilerRT;
   } else if (LibName == "libgcc")
     unwindLibType = ToolChain::UNW_Libgcc;
+  else if (LibName == "vcruntime")
+    unwindLibType = ToolChain::UNW_Vcruntime;
   else {
     if (A)
       getDriver().Diag(diag::err_drv_invalid_unwindlib_name)
@@ -1152,6 +1156,8 @@ ToolChain::CXXStdlibType ToolChain::GetCXXStdlibType(const ArgList &Args) const{
     cxxStdlibType = ToolChain::CST_Libcxx;
   else if (LibName == "libstdc++")
     cxxStdlibType = ToolChain::CST_Libstdcxx;
+  else if (LibName == "stl")
+    cxxStdlibType = ToolChain::CST_Stl;
   else if (LibName == "platform")
     cxxStdlibType = GetDefaultCXXStdlibType();
   else {
@@ -1290,6 +1296,9 @@ void ToolChain::AddCXXStdlibLibArgs(const ArgList &Args,
   case ToolChain::CST_Libstdcxx:
     CmdArgs.push_back("-lstdc++");
     break;
+
+  default:
+    break;
   }
 }