Driver: Implement JoinedAndSeparateArg::getValue and add parsing test
case.

llvm-svn: 67151
diff --git a/clang/lib/Driver/Arg.cpp b/clang/lib/Driver/Arg.cpp
index 625e784..6cff93e 100644
--- a/clang/lib/Driver/Arg.cpp
+++ b/clang/lib/Driver/Arg.cpp
@@ -142,6 +142,7 @@
 const char *JoinedAndSeparateArg::getValue(const ArgList &Args, 
                                            unsigned N) const {
   assert(N < getNumValues() && "Invalid index.");
-  assert(0 && "FIXME: Implement");
-  return 0;
+  if (N == 0)
+    return Args.getArgString(getIndex()) + strlen(getOption().getName());
+  return Args.getArgString(getIndex() + 1);
 }