clang-cl: Don't pass /defaultlib to the linker

Since r187945, clang-cl will add the runtime library dependency to
the .obj file.

llvm-svn: 188086

clang/lib/Driver/Tools.cpp

@@ -6552,7 +6552,8 @@ void visualstudio::Link::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   if (!Args.hasArg(options::OPT_nostdlib) &&
-    !Args.hasArg(options::OPT_nostartfiles)) {
+      !Args.hasArg(options::OPT_nostartfiles) &&
+      !C.getDriver().IsCLMode()) {
     CmdArgs.push_back("-defaultlib:libcmt");
   }