[Frontend] NFC: Add a flag to explicitly disable DynamicActorIsolation feature

Author: xedin

include/swift/Basic/LangOptions.h

@@ -593,6 +593,9 @@ namespace swift {
     /// type-checking, SIL verification, and IR emission,
     bool BypassResilienceChecks = false;
 
+    /// Disables `DynamicActorIsolation` feature.
+    bool DisableDynamicActorIsolation = false;
+
     /// Whether or not to allow experimental features that are only available
     /// in "production".
 #ifdef NDEBUG

include/swift/Option/Options.td

@@ -817,6 +817,11 @@ def disable_actor_data_race_checks :
   Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
   HelpText<"Disable runtime checks for actor data races">;
 
+def disable_dynamic_actor_isolation :
+  Flag<["-"], "disable-dynamic-actor-isolation">,
+  Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Disable dynamic actor isolation checks">;
+
 def enable_bare_slash_regex : Flag<["-"], "enable-bare-slash-regex">,
   Flags<[FrontendOption, ModuleInterfaceOption]>,
   HelpText<"Enable the use of forward slash regular-expression literal syntax">;

lib/Driver/ToolChains.cpp

@@ -264,6 +264,7 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
   inputArgs.AddLastArg(arguments,
                        options::OPT_enable_actor_data_race_checks,
                        options::OPT_disable_actor_data_race_checks);
+  inputArgs.AddLastArg(arguments, options::OPT_disable_dynamic_actor_isolation);
   inputArgs.AddLastArg(arguments, options::OPT_warn_concurrency);
   inputArgs.AddLastArg(arguments, options::OPT_strict_concurrency);
   inputArgs.AddAllArgs(arguments, options::OPT_enable_experimental_feature);

lib/Frontend/CompilerInvocation.cpp

@@ -1513,6 +1513,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     }
   }
 
+  Opts.DisableDynamicActorIsolation |=
+      Args.hasArg(OPT_disable_dynamic_actor_isolation);
+
 #if SWIFT_ENABLE_EXPERIMENTAL_PARSER_VALIDATION
   /// Enable round trip parsing via the new swift parser unless it is disabled
   /// explicitly. The new Swift parser can have mismatches with C++ parser -