[Driver] Use UniversalCRT on Windows if available

Summary:
With Visual Studio 2015 release, a part of runtime library was extracted
and now comes with Windows Kits. This patch enables clang to use
Universal CRT library if  %INCLUDE or %LIB environment varaibles are not
specified.

See also https://llvm.org/bugs/show_bug.cgi?id=24741

Patch by Igor Kudrin

Reviewers: zturner, hans, rnk

Subscribers: ruiu, cfe-commits

Differential Revision: http://reviews.llvm.org/D12695

llvm-svn: 247362

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index eca599297b6..7c859850592 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -8948,6 +8948,13 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       }
       CmdArgs.push_back(
           Args.MakeArgString(std::string("-libpath:") + LibDir.c_str()));
+
+      if (MSVC.useUniversalCRT(VisualStudioDir)) {
+        std::string UniversalCRTLibPath;
+        if (MSVC.getUniversalCRTLibraryPath(UniversalCRTLibPath))
+          CmdArgs.push_back(Args.MakeArgString(std::string("-libpath:") +
+                                               UniversalCRTLibPath.c_str()));
+      }
     }
 
     std::string WindowsSdkLibPath;