druntime build is broken on Win_32

[tsbockman via Digitalmars-d]

Error: don't know how to make 'import\core\sys\linux\stdio.d'
Possibly caused by: 
https://github.com/D-Programming-Language/druntime/pull/1404/files#diff-7d40e7eb04757040e0db6ec6923cd026L50