[Exclusivity] Put suppression for free function swap() behind a flag

And leave suppression off by default for now. We'll use this to evaluate
how often swap() causes exclusivity conflicts to be reported.

lib/Frontend/CompilerInvocation.cpp

@@ -1324,6 +1324,8 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
     |= Args.hasArg(OPT_assume_parsing_unqualified_ownership_sil);
   Opts.EnableMandatorySemanticARCOpts |=
       !Args.hasArg(OPT_disable_mandatory_semantic_arc_opts);
+  Opts.SuppressStaticExclusivitySwap |=
+      Args.hasArg(OPT_suppress_static_exclusivity_swap);
 
   if (Args.hasArg(OPT_debug_on_sil)) {
     // Derive the name of the SIL file for debugging from