Directions on compiling the right files

[Fabrício Zimmerer Murta]

Hello,

   I am a bit lost here. We recently started a project using GNU Build 
System in order to make our package installable everywhere without mysteries 
of package-specific builds.
   Now I am facing a problem I will try to explain with an easier to 
understand example.
   Suppose I am making an application and it currently supports Linux 
system. Now suppose I am to add Windows access and this would imply adding 
some source files for windows-specific routines and removing some 
linux-specific routines. Some of the work can be done via preprocessor 
macros. But if some .c files are not to be compiled at all, I could either 
remove the entire file via macros, but I doubt I will get any .o out of 
these empty files, and I will not want to include these .o's in the linking 
phase.
   In other words, there will be new .c files that should be compiled only 
for the windows version and some .c files exclusive to the linux version.
   Suppose also I want to specify this at configure-time (e.g. 
"./configure" builds linux, "./configure --enable-win32" builds windows).
   I know I can do this on configure.ac, but I don't know, at configure 
time, how would I change the Makefile's dependencies for each of these two 
builds. Any directions on how to do this (pointing a relatively simple 
package that does this also can help a lot) are very well accepted!

Thank you,
Fabricio Murta