compilation failure

[barak]

After allowing g++ to default. This is on a stock Debian "testing" amd64 machine, with qt5-default installed.

$ g++ --version
g++ (Debian 8.2.0-21) 8.2.0

$ qmake --version
QMake version 3.1
Using Qt version 5.11.3 in /usr/lib/x86_64-linux-gnu

$ qmake; make -j1 -k
[...]
g++ -c -pipe -std=c++14 -Wall -Wextra -Wshadow -g -O2 -std=gnu++1y -Wall -W -D_REENTRANT -fPIC -DVERSION_STRING=\"0.3.0\" -DQT_NO_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I. -IOURCE_DIR -isystem /usr/include/x86_64-linux-gnu/qt5 -isystem /usr/include/x86_64-linux-gnu/qt5/QtWidgets -isystem /usr/include/x86_64-linux-gnu/qt5/QtGui -isystem /usr/include/x86_64-linux-gnu/qt5/QtCore -Iobj -isystem /usr/include/libdrm -I/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-g++ -o obj/board_size_dialog.o ui/board_size_dialog.cpp
ui/board_size_dialog.cpp:2:10: fatal error: ui_board_size_dialog.h: No such file or directory
 #include "ui_board_size_dialog.h"
          ^~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [Makefile:486: obj/board_size_dialog.o] Error 1
g++ -c -pipe -std=c++14 -Wall -Wextra -Wshadow -g -O2 -std=gnu++1y -Wall -W -D_REENTRANT -fPIC -DVERSION_STRING=\"0.3.0\" -DQT_NO_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I. -IOURCE_DIR -isystem /usr/include/x86_64-linux-gnu/qt5 -isystem /usr/include/x86_64-linux-gnu/qt5/QtWidgets -isystem /usr/include/x86_64-linux-gnu/qt5/QtGui -isystem /usr/include/x86_64-linux-gnu/qt5/QtCore -Iobj -isystem /usr/include/libdrm -I/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-g++ -o obj/mainwindow.o ui/mainwindow.cpp
ui/mainwindow.cpp:2:10: fatal error: ui_mainwindow.h: No such file or directory
 #include "ui_mainwindow.h"
          ^~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [Makefile:504: obj/mainwindow.o] Error 1
make: Target 'first' not remade because of errors.