Is there a way to do a conditional compilation according to environment variables with qmake:

I am trying to recreate the following:

ifdef AMDAPPSDKROOT
INC_DIRS = "$(AMDAPPSDKROOT)include"
endif

ifdev NVSDKCOMPUTE_ROOT
INC_DIRS = "$(NVSDKCOMPUTE_ROOT)\OpenCL\common\inc"
endif

Also there is another problem

Even though I have done this:
INCLUDEPATH += "$NVSDKCOMPUTE_ROOT\OpenCL\common\inc"

where NVSDKCOMPUTE_ROOT is "C:\ProgramData\NVIDIA Corporation\NVIDIA GPU Computing SDK 4.2"

Even though I use double quotes, the gcc gets the path as separate words. Actually that part \NVIDIA Corporation\ is OK but the next: NVIDIA GPU Computing SDK 4.2 gets split into five words and causes errors. Why don't the double quotes work? My workaround was to copy these files to a folder without white spaces for now. Is this a bug or a feature.

I would like my project file to compile on 3-4 different configurations: Linux 32/64bit, Windows 7 32/64 bit with NVIDIA SDK or AMD SDK respectively depending on the available hardware.