Fix a problem when cross compiling using NMake.
Fix a problem when cross compiling using NMake.

The previous behaviour was to add a CXX flags when
msdev/devenv/nmake/VCExpress was detected.
However these tools have nothing to do with the compiler used.
The /W4 applies only when CL (aka MS-VC) is the current compiler.
It avoids a compilation issue when nmake is used with another
toolchain than the MS one (eg. the Android NDK which is base on GCC,
and of course GCC do not know the /W4 flag!).
Use MSVC instead of MSVC_VERSION variable to do the test.

Change-Id: I287796dcba9c39a8f912db10bd8b8f527a544bdb

sankhesh/VTK,johnkit/vtk-dev,msmolens/VTK,sumedhasingla/VTK,berendkleinhaneveld/VTK,candy7393/VTK,msmolens/VTK,sankhesh/VTK,ashray/VTK-EVM,sankhesh/VTK,jmerkow/VTK,gram526/VTK,johnkit/vtk-dev,sankhesh/VTK,demarle/VTK,gram526/VTK,keithroe/vtkoptix,ashray/VTK-EVM,collects/VTK,msmolens/VTK,SimVascular/VTK,gram526/VTK,candy7393/VTK,msmolens/VTK,SimVascular/VTK,sankhesh/VTK,collects/VTK,johnkit/vtk-dev,msmolens/VTK,SimVascular/VTK,keithroe/vtkoptix,sumedhasingla/VTK,SimVascular/VTK,gram526/VTK,berendkleinhaneveld/VTK,SimVascular/VTK,johnkit/vtk-dev,mspark93/VTK,berendkleinhaneveld/VTK,mspark93/VTK,jmerkow/VTK,ashray/VTK-EVM,jmerkow/VTK,biddisco/VTK,mspark93/VTK,mspark93/VTK,candy7393/VTK,biddisco/VTK,demarle/VTK,berendkleinhaneveld/VTK,mspark93/VTK,ashray/VTK-EVM,keithroe/vtkoptix,ashray/VTK-EVM,sumedhasingla/VTK,mspark93/VTK,hendradarwin/VTK,sumedhasingla/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,demarle/VTK,hendradarwin/VTK,msmolens/VTK,collects/VTK,johnkit/vtk-dev,sumedhasingla/VTK,gram526/VTK,sumedhasingla/VTK,biddisco/VTK,jmerkow/VTK,sumedhasingla/VTK,collects/VTK,biddisco/VTK,gram526/VTK,biddisco/VTK,candy7393/VTK,candy7393/VTK,ashray/VTK-EVM,biddisco/VTK,gram526/VTK,candy7393/VTK,jmerkow/VTK,demarle/VTK,sumedhasingla/VTK,msmolens/VTK,keithroe/vtkoptix,hendradarwin/VTK,collects/VTK,jmerkow/VTK,ashray/VTK-EVM,mspark93/VTK,keithroe/vtkoptix,demarle/VTK,sankhesh/VTK,johnkit/vtk-dev,keithroe/vtkoptix,sankhesh/VTK,gram526/VTK,SimVascular/VTK,msmolens/VTK,berendkleinhaneveld/VTK,candy7393/VTK,sankhesh/VTK,hendradarwin/VTK,demarle/VTK,jmerkow/VTK,keithroe/vtkoptix,demarle/VTK,keithroe/vtkoptix,SimVascular/VTK,berendkleinhaneveld/VTK,hendradarwin/VTK,SimVascular/VTK,ashray/VTK-EVM,collects/VTK,biddisco/VTK,demarle/VTK,johnkit/vtk-dev,hendradarwin/VTK,candy7393/VTK,mspark93/VTK,hendradarwin/VTK