Singleobj builds

[Johan Engelen via digitalmars-d-ldc]

Hi all,
   I just found this in mars.d:
```
   version (IN_LLVM)
   {
     if (global.params.oneobj && modules.dim < 2)
         global.params.oneobj = false;
```

Is there a special reason why `oneobj` is set to false when we 
only pass one D source file? For caching work, I want to know 
whether we are building stuff into one object file, and 
params.oneobj is apparently not what it says it is ;)

Thanks,
   Johan