Xcode: Internally uses -S instead of -H to specify source directory

This was accidentally left out of commit de962cc00d (CMake: Internally
uses -S instead of -H to specify source directory, 2018-09-06,
v3.13.0-rc1~76^2~1).

Source/cmGlobalXCodeGenerator.cxx

@@ -756,7 +756,7 @@ void cmGlobalXCodeGenerator::CreateReRunCMakeFile(
   makefileStream << "\t"
                  << this->ConvertToRelativeForMake(
                       cmSystemTools::GetCMakeCommand())
-                 << " -H"
+                 << " -S"
                  << this->ConvertToRelativeForMake(root->GetSourceDirectory())
                  << " -B"
                  << this->ConvertToRelativeForMake(root->GetBinaryDirectory())