[PATCH] Add option to use temporary file for assembling with clang

[David Peixotto]

> What's the value in this flag?
> 
> If it's only for testing, normal test cases would just do this as two
> commands (emit the asm, then run llc on the asm)
> 
>  I'm guessing you want this so you could test the correctness of the
> integrated assembler over a large codebase using an existing build system?

Yes, that's correct. I needed to verify that the integrated assembler works
over a large source base and this flag makes it easy to do that. I thought I
would post it to the community to see if others thought it is a useful
addition.