[PlistSupport] Produce a newline to end plist output files

[hubert.reinterpretcast]

Summary

As suggested in the review of D62949, this patch updates the plist output to have a newline at the end of the file. This makes it so that the plist output file qualifies as a POSIX text file, which increases the consumability of the generated plist file in relation to various tools.

[xingxue]

LGTM.

[NoQ]

Thanks!

lib/ARCMigrate/PlistReporter.cpp

for (ArrayRef<StoredDiagnostic>::iterator
 
     // Close up the entry.
     o << "  </dict>\n";
   }
 
   o << " </array>\n";
 
   // Finish.
-  o << "</dict>\n</plist>";
+  o << "</dict>\n</plist>\n";
 }

lib/StaticAnalyzer/Core/PlistDiagnostics.cpp

if (llvm::AreStatisticsEnabled() && AnOpts.ShouldSerializeStats) {
     std::string stats;
     llvm::raw_string_ostream os(stats);
     llvm::PrintStatisticsJSON(os);
     os.flush();
     EmitString(o, html::EscapeText(stats)) << '\n';
   }
 
   // Finish.
-  o << "</dict>\n</plist>";
+  o << "</dict>\n</plist>\n";
 }
 
 //===----------------------------------------------------------------------===//
 // Declarations of helper functions and data structures for expanding macros.
 //===----------------------------------------------------------------------===//
 
 namespace {