[SYCL][Windows] Improve windows sycl.lib linking

This patch does two things, first it makes `-fsycl` ignore `-nostdlib`
when linking the SYCL library. This is necessary because for Clang on
Windows CMake will generate link commands using `-nostdlib` and
explicitly list the system libraries, but of course it doesn't do it for
SYCL, so we currently end up never linking the SYCL library when this is
used.

Ignoring `-nostdlib` for `-fsycl` on Windows seems like a reasonnable
solution for this as this is also what is done for the OpenMP runtime
libraries.

See the CMake module:
* https://github.com/Kitware/CMake/blob/aa2de7cd2a04699744a224ab84e0ca483559c5d3/Modules/Platform/Windows-Clang.cmake#L79

In addition this patch also adds a linker parameter to help clang find
the `sycl.lib` file without requiring users to tweak their environments
to link against it.

Author: npmiller

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -131,10 +131,11 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-defaultlib:oldnames");
   }
 
-  if ((!C.getDriver().IsCLMode() && !Args.hasArg(options::OPT_nostdlib) &&
-       Args.hasArg(options::OPT_fsycl) &&
+  if ((!C.getDriver().IsCLMode() && Args.hasArg(options::OPT_fsycl) &&
        !Args.hasArg(options::OPT_nolibsycl)) ||
       Args.hasArg(options::OPT_fsycl_host_compiler_EQ)) {
+    CmdArgs.push_back(Args.MakeArgString(std::string("-libpath:") +
+                                         TC.getDriver().Dir + "/../lib"));
     if (Args.hasArg(options::OPT__SLASH_MDd))
       CmdArgs.push_back("-defaultlib:sycld.lib");
     else