Keeping build systems separate?

I've been placing any code changes I've made within #ifdef __APPLE__  
statements, but I'm wondering if this is the correct approach.  I  
prevents conflicts on non-apple systems, but not between build systems  
on apples.  Is there a set way that I should be segretating changes  
made for a specific build system?  like using "HAVE_XCODE_BUILD"  
instead of "__APPLE__"?

thanks for any advice on this.

laters,
Tom


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