Build qtdeclarative fail on Ubuntu 14.04

Question

I try to build qtdeclarative from source code but an compilation error occured

fatal error: QtCore/private/qglobal_p.h: No such file or directory.

Below is some information about my situation

1. OS: Ubuntu 14.04

2. Build Steps

   • Install qt5 library

     $ sudo apt-get install qt5-default

   • Getting the qtbase source

     $ mkdir qt; cd qt

     $ git clone git://code.qt.io/qt/qtbase.git

   • Build the qtbase source

     $ export QTVER=qt5

     $ export QTDIR=/opt/qt/$QTVER

     $ export PATH=$QTDIR/bin/:$PATH

     $ export LD_LIBRARY_PATH=$QTDIR/lib/:$LD_LIBRARY_PATH

     $ export PKG_CONFIG_PATH=$QTDIR/lib/pkgconfig/:$PKG_CONFIG_PATH

     $ export QT_PLUGIN_PATH=$QTDIR/lib/plugins

     $cd qtbase

     $ ./configure -confirm-license -opensource -debug -nomake examples -nomake tests -make libs -prefix ${QTDIR}

     $ make

     $ sudo make install

     => Build success

   • Getting the qtdeclarative source

     $ cd ..

     $ mkdir qtdeclarative; cd qtdeclarative

     $ git clone git://code.qt.io/qt/qtdeclarative.git

   • Build the qtdeclarative source

     $ qmake

     $ make

==> ERROR at this step

fatal error: QtCore/private/qglobal_p.h: No such file or directory.

What did i do wrong or missing something ?