[frontend] Add support for parsing ImmediateArgv.

These are not yet used, since the integrated frontend doesn’t yet support immediate mode, but they are ready for use once immediate mode is supported.

Swift SVN r11326

lib/Frontend/CompilerInvocation.cpp

@@ -83,6 +83,12 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
     Opts.ModuleSourceListPath = A->getValue();
   }
 
+  if (const Arg *A = Args.getLastArg(OPT__DASH_DASH)) {
+    for (unsigned i = 0, e = A->getNumValues(); i != e; ++i) {
+      Opts.ImmediateArgv.push_back(A->getValue(i));
+    }
+  }
+
   return false;
 }