[CMake] Passing environment variables in Windows

[Bill Hoffman]

Leo Breebaart wrote:
> Sorry, I probably should have mentioned it, but didn't want to
> clutter up my original mail with a list of all the things I tried
> that did not work. That was one of 'em. :-)
> 
>> But if you want it to run at custom command time, you would
>> have to do it as a cmake script. Currently there is not a way
>> to set environment variables to be used during the running of
>> custom commands without creating a cmake script.
> 
> I was afraid of that, but it's good to have it confirmed. Thanks!
> 
The real issue is build time vs CMake time.  At CMake time we can set 
env vars pretty easy.  However, by the time the build is running, the 
CMake process is long gone along with its environment...  The CMake 
scripts are cross platform.

-Bill