[vtkusers] How to build libraries for both 32-bit and 64-bit architectures

[Elvis Dowson]

Hi,
         I've just run into a bit of problem with building some  
dependent libraries.

Here is my situation, I have libpng-1.2.31 which is used by  
paraview-3.x.x, vtk-5.x and qt-4.5.x.

For paraview, I need the 32-bit version of libpng.

For qt-4.5.x 64-bit, vtk-5.3.x 64-bit and to use the Cocoa framework,  
I need a 64-bit version of libpng.

I first built paraview with the 32-bit version of libpng, and it ran  
correctly.

Then for my qt-4.5.x and vtk-5.x 64-bit compilation tests, I was  
forced to rebuild and install the 64-bit version of libpng. When i ran  
sudo make install, it copied the 64-bit version of the libraries and  
paraview stopped working.

Could someone please tell me what I should do to manage a libpng  
installation that can support both 32-bit and 64-bit architectures?

When I run ./configure --help I get the following information:

Installation directories:
   --prefix=PREFIX         install architecture-independent files in  
PREFIX
                           [/usr/local]
   --exec-prefix=EPREFIX   install architecture-dependent files in  
EPREFIX
                           [PREFIX]

What is the --exec-prefix for ?

Best regards,

Elvis Dowson