Add PNaCl support for VS addin.

visual_studio/NativeClientVSAddIn/NaCl.Build.CPPTasks/GCCUtilities.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
 using System.IO;
 using System.Text.RegularExpressions;
 
 namespace NaCl.Build.CPPTasks
 {
     class GCCUtilities
     {
         public const int s_CommandLineLength = 256;
 
+        /// <summary>
+        /// Find python executable in user's PATH.
+        /// </summary>
+        public static bool FindPython()
+        {
+            string envvar = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Process);
+            List<string> pathList = new List<string>(envvar.Split(';'));
+            foreach (string path in pathList)
+            {
+                string testPath = Path.Combine(path, "python.bat");
+                if (File.Exists(testPath))
+                {
+                    return true;
+                }
+                testPath = Path.Combine(path, "python.exe");
+                if (File.Exists(testPath))
+                {
+                    return true;
+
+                }
+            }
+            return false;
+        }
+
         public static string ConvertPathWindowsToPosix(string path)
         {
             return path.Replace('\\', '/');
         }
 
         public static string ConvertPathPosixToWindows(string path)
         {
             path = path.Replace('/', '\\');
             // also make double backslashes a single slash
             // TODO: speed this up by iterating instead of two replaces
@@ skipping 67 matching lines @@
             },
             new GCCRegexLineConverter
             {
                 OutputExpression =      new Regex(@"^\s*(.?.?[^:]*.*?):(.?.?[^:]*.*?):([1-9]\d*):(.*$)"),
                 FilenameIdentifier =    @"$2",
                 RemainderIdentifier =   @"($3):'$1' $4"
             }
         };
     } // GCCUtilities
 } // namespace