[interop][SwiftToCxx] fix the source compat failures

Author: hyp

lib/PrintAsClang/PrintAsClang.cpp

@@ -52,13 +52,15 @@ static void emitObjCConditional(raw_ostream &out,
 }
 
 static void writePtrauthPrologue(raw_ostream &os) {
-  os << "#if __has_include(<ptrauth.h>)\n";
-  os << "# include <ptrauth.h>\n";
-  os << "#else\n";
-  os << "# ifndef __ptrauth_swift_value_witness_function_pointer\n";
-  os << "#  define __ptrauth_swift_value_witness_function_pointer(x)\n";
-  os << "# endif\n";
-  os << "#endif\n";
+  emitCxxConditional(os, [&]() {
+    os << "#if __has_include(<ptrauth.h>)\n";
+    os << "# include <ptrauth.h>\n";
+    os << "#else\n";
+    os << "# ifndef __ptrauth_swift_value_witness_function_pointer\n";
+    os << "#  define __ptrauth_swift_value_witness_function_pointer(x)\n";
+    os << "# endif\n";
+    os << "#endif\n";
+  });
 }
 
 static void writePrologue(raw_ostream &out, ASTContext &ctx,

test/PrintAsCxx/empty.swift

@@ -35,13 +35,15 @@
 // CHECK-NEXT:  #include <stdbool.h>
 // CHECK-NEXT:  #include <string.h>
 // CHECK-NEXT:  #endif
+// CHECK-NEXT:  #if defined(__cplusplus)
 // CHECK-NEXT:  #if __has_include(<ptrauth.h>)
 // CHECK-NEXT:  # include <ptrauth.h>
 // CHECK-NEXT:  #else
 // CHECK-NEXT:  # ifndef __ptrauth_swift_value_witness_function_pointer
 // CHECK-NEXT:  #  define __ptrauth_swift_value_witness_function_pointer(x)
 // CHECK-NEXT:  # endif
 // CHECK-NEXT:  #endif
+// CHECK-NEXT:  #endif
 
 // CHECK-LABEL: !defined(SWIFT_TYPEDEFS)
 // CHECK-NEXT:  # define SWIFT_TYPEDEFS 1