Android – “Cannot find build.xml” error building Android SDK sample

androidant

The log is:

BUILD FAILED

/Users/xxx/sample/build.xml:114: Cannot find /Users/xxx/Library/Android/Library/Android/sdk/tools/ant/build.xml imported from /Users/xxx/sample/build.xml

I can confirm that sdkdir is right.

I found there is not an ant directory in /Users/xxx/Library/Android/Library/Android/sdk/tools/.

I found someone saying it is automatically generated. How can I make this build.xml in tools/ant? I use a Mac.