[CMake] windows nmake build performance (specifically checking for built targets)

[Kevin Burge]

I have many built targets.  When I do "nmake install" it takes a long 
time between each "Built target..." check (extremely long, compared to 
using make on a Unix box).  Is there any way to speed this up?  It's 
particularly slow on built C++ targets.  It can take between 2-5 seconds 
before it moves to the next target.

cmake280rc5 on the same hardware smokes the paints off of nmake "Built 
target" messages.

Linux: 5 seconds to show all built targets
Windows: 61 seconds to show all built targets.

Thanks,
Kevin