osx - Qt running error Executable does not exist -

i trying learn qt creator.

i installed version 5 on mac osx , tried build simple project found on book.

the project @ first compiled , run correctly tried clean all , build all. @ point seems compile correctly, when try run it, getting following error: "executable /users/mymac/build-project_name-desktop_qt_5_5_1_clang_64bit-debug/project_name.app/contents/macos/project_name not exist".

notice project folder /users/mymac/project_name

i had modify file *.pro adding qt += widgets because got target empty error.

i tried older questions did not find useful.

here .pro file:

###################################################################### # automatically generated qmake (2.01a) sun mar 20 21:45:06 2016 ###################################################################### qt += widgets template = app target =  dependpath += . includepath += .  # input headers += finddialog.h mainwindow.h forms += mainwindow.ui sources += finddialog.cpp main.cpp mainwindow.cpp` 

thanks in advance.