Add better error message on missing build-tools, include other versions.

lib/devices/android/adb.js

@@ -68,21 +68,31 @@ ADB.prototype.checkSdkBinaryPresent = function (binary, cb) {
   }
   if (this.sdkRoot) {
     var binaryLocs = [ path.resolve(this.sdkRoot, "platform-tools", binaryName)
-        , path.resolve(this.sdkRoot, "tools", binaryName)
-        , path.resolve(this.sdkRoot, "build-tools", "17.0.0", binaryName)
-        , path.resolve(this.sdkRoot, "build-tools", "android-4.2.2", binaryName)
-        , path.resolve(this.sdkRoot, "build-tools", "18.0.1", binaryName)
-        , path.resolve(this.sdkRoot, "build-tools", "android-4.3", binaryName)
-        , path.resolve(this.sdkRoot, "build-tools", "android-4.4", binaryName)
-        , path.resolve(this.sdkRoot, "build-tools", "19.0.0", binaryName)];
+        , path.resolve(this.sdkRoot, "tools", binaryName) ];
+
+    // put supported build tool dir names here
+    var supportedBuildToolDirs = [ '17.0.0'
+        , '18.0.1'
+        , '19.0.0'
+        , '19.0.1'
+        , 'android-4.2.2'
+        , 'android-4.3'
+        , 'android-4.4' ];
+    // add the possible paths for supported build tools
+    _.each(supportedBuildToolDirs, function (versionDir) {
+        binaryLocs.push(path.resolve(this.sdkRoot, "build-tools", versionDir, binaryName));
+      }.bind(this));
+
     _.each(binaryLocs, function (loc) {
       if (fs.existsSync(loc)) binaryLoc = loc;
     });
 
     if (binaryLoc === null) {
       cb(new Error("Could not find " + binary + " in tools, platform-tools, " +
-                   "or build-tools under \"" + this.sdkRoot + "\"; " +
-                   "do you have android SDK installed into this location?"));
+                   "or supported build-tools under \"" + this.sdkRoot + "\"; " +
+                   "do you have android SDK or build-tools installed into this " +
+                   "location? Supported build tools are: " +
+                   supportedBuildToolDirs.join(', ')));
       return;
     }
     this.debug("Using " + binary + " from " + binaryLoc);