Failed to create xcodebuild build xcode project with dependent project. dependent project goal not found

Question

My main project called sample.xcodeproj depends on sdklib.xcodeproj. The purpose of sdklib.xocdeproj is sdk.a.

when i create sample.xcodeproj with xcodebuild command

xcodebuild -project sample.xcodeproj 

Failed.

  error: no such file or directory:'/Users/.../libsdklib.a 

It seems that the dependent project is not built. I also did not see libsdklib.a in the sdklib.xcodeproj target path. But it works well in xcode. So where is sdk.a when I create sample.xcodeproj? and how can I use the xcodebuild command to build sample.xcodeproj using sdklib.xcodeproj?