-native self compile problems

[Matthew Fluet]

> > That's a known bug, with a really simple fix.  In x86-codegen.fun, the
> > outputAssembly function doesn't call  done ()  before it loops to a new
> > assembly file.  That leaves the file open and unflushed, which causes
> > these strange errors when the assembler hits it.  Here's the correct
> > version of the function:
> 
> Thanks.  My bad.  I've added the new outputAssembly.

Don't worry, I introduced it when I rewrote the outputAssembly function.
The old version had the possibility that a new assembly file would be
opened even if there were no chunks left to process.