[QNX] qtcreator should use qnxenv with lupdate

If lupdate is run with QNX kit, it gives the following error:

"C:\Qt\Qt5.7.0\5.7\mingw53_32\bin\lrelease.exe" finished
Starting external tool "C:\Qt\Qt5.7.0\5.7\qnx6_x86\bin\lupdate.exe"
C:/Git/master-gui/gui/gui.pro
WARNING: Project ERROR: QNX_TARGET environment variable not set
WARNING: Could not read qmake configuration file
C:/Qt/Qt5.7.0/5.7/qnx6_x86/mkspecs/qnx-x86-qcc/qmake.conf."

The workaround is to set the QNX_TARGET and path for lupdate in QtCreator, but then switching between kits and running lupdate may not work.