Project file variable that defines the build path

Hello,

I am looking for the Qt project file variable to use in order to specify the build path.
In my example below I would like to replace build-Wokspace-Desktop_Qt_5_8_0_MSVC2015_64bit-Debug by a variable as this depends on the Qt version, on the build (debug,release) version, on the compiler used, on the target platform.

Code:

QT       += core widgets
 
TARGET = pluginDemo
TEMPLATE = app
 
SOURCES   += main.cpp \
             mainwindow.cpp
#             pluginDialog.cpp
 
HEADERS   += mainwindow.h
#             pluginDialog.h
 
RESOURCES += res/icons.qrc
 
win32:CONFIG(release, debug|release): LIBS += -L$$PWD/../../../build-Wokspace-Desktop_Qt_5_8_0_MSVC2015_64bit-Debug/src/libs/extensionsystem/release/ -lExtensionSystem
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/../../../build-Wokspace-Desktop_Qt_5_8_0_MSVC2015_64bit-Debug/src/libs/extensionsystem/debug/ -lExtensionSystem
else:unix: LIBS += -L$$PWD/../../../build-Wokspace-Desktop_Qt_5_8_0_MSVC2015_64bit-Debug/src/libs/extensionsystem/ -lExtensionSystem
 
INCLUDEPATH += $$PWD/../../libs/extensionsystem
DEPENDPATH += $$PWD/../../libs/extensionsystem