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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187945 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 27ddd84..a4c93fa 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -502,6 +502,8 @@
     }
   }
 
+  Opts.DependentLibraries = Args.getAllArgValues(OPT_dependent_lib);
+
   return Success;
 }