Small rdmd wrapper for windows

[Steve Biedermann via Digitalmars-d-announce]

On Thursday, 31 March 2016 at 10:54:50 UTC, Kagamin wrote:
> Maybe rdmd should parse D_INCLUDE_PATH itself? Then it would 
> work on its own.

You could also use the DFLAGS environment variable for that, but 
I think it's cleaner to seperate the scripting environment from 
the normal build environment.