Prefer ChakraHost when available to node and WScript

Author: mihailik

src/compiler/sys.ts

@@ -642,17 +642,17 @@ namespace ts {
  };
  }
 
- if (typeof WScript !== "undefined" && typeof ActiveXObject === "function") {
+ if (typeof ChakraHost !== "undefined") {
+ return getChakraSystem();
+ }
+ else if (typeof WScript !== "undefined" && typeof ActiveXObject === "function") {
  return getWScriptSystem();
  }
  else if (typeof process !== "undefined" && process.nextTick && !process.browser && typeof require !== "undefined") {
  // process and process.nextTick checks if current environment is node-like
  // process.browser check excludes webpack and browserify
  return getNodeSystem();
  }
- else if (typeof ChakraHost !== "undefined") {
- return getChakraSystem();
- }
  else {
  return undefined; // Unsupported host
  }