(GH-1239) Report process id in log files

In detecting multiple processes overlapping each other in the log, it
becomes difficult when that information is not shown in the log. Report
the process id in the log file as well to bring more visibility to
whether multiple processes are running a command.

src/chocolatey/infrastructure/logging/Log4NetAppenderConfiguration.cs

@@ -44,6 +44,8 @@ public sealed class Log4NetAppenderConfiguration
         /// <param name="outputDirectory">The output directory.</param>
         public static void configure(string outputDirectory = null)
         {
+            GlobalContext.Properties["pid"] = System.Diagnostics.Process.GetCurrentProcess().Id;
+
             var assembly = Assembly.GetExecutingAssembly();
             var resource = ApplicationParameters.Log4NetConfigurationResource;
             if (Platform.get_platform() != PlatformType.Windows)
@@ -75,7 +77,7 @@ private static void set_file_appender(string outputDirectory)
 
                 var layout = new PatternLayout
                     {
-                        ConversionPattern = "%date [%-5level] - %message%newline"
+                        ConversionPattern = "%date %property{pid} [%-5level] - %message%newline"
                     };
                 layout.ActivateOptions();