newline feed in compiler command line params causes undefined behavior

Example:

```
[<MsvcWin (""" /I 
..\include\SDL2 /I 
..\include ..\lib\win\x64\SDL2.lib 
..\lib\win\x64\SDL2main.lib ..\lib\win\x64\glew32.lib opengl32.lib """)>]
```

... causes very mysterious behaviors.
