clang-cl: Support the run-time selection options (/MD, /MT et al.)

These flags set some preprocessor macros and injects a dependency
on the runtime library into the object file, which later is picked up
by the linker.

This also adds a new CC1 flag for adding a dependent library.

Differential Revision: http://llvm-reviews.chandlerc.com/D1315

llvm-svn: 187945

clang/lib/Frontend/CompilerInvocation.cpp

@@ -502,6 +502,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
     }
   }
 
+  Opts.DependentLibraries = Args.getAllArgValues(OPT_dependent_lib);
+
   return Success;
 }