[immediate] Load Foundation early enough for bridging

Foundation needs to be loaded early in the process for Swift's runtime
to properly initialize bridging support; otherwise it may cause issues
like unrecognized selectors. When scripting, load Foundation early in
performFrontend before any swift code runs.

rdar://129528115

lib/FrontendTool/FrontendTool.cpp

@@ -1955,6 +1955,13 @@ int swift::performFrontend(ArrayRef<const char *> Args,
     return finishDiagProcessing(1, /*verifierEnabled*/ false);
   }
 
+  // Scripts that use the Foundation framework need it loaded early for bridging
+  // to work correctly on Darwin platforms. On other platforms this is a no-op.
+  if (Invocation.getFrontendOptions().RequestedAction ==
+      FrontendOptions::ActionType::Immediate) {
+    loadFoundationIfNeeded(Instance->getDiags());
+  }
+
   // Don't ask clients to report bugs when running a script in immediate mode.
   // When a script asserts the compiler reports the error with the same
   // stacktrace as a compiler crash. From here we can't tell which is which,