[lld] r189826 - Add support for --sysroot.

[Joerg Sonnenberger]

On Tue, Sep 03, 2013 at 09:55:30AM -0700, Rui Ueyama wrote:
> > +def sysroot : Joined<["--"], "sysroot=">,
> > +    HelpText<"Set the system root">;
> >
> 
> Could this handle --sysroot *dirname* as well as --sysroot=*dirname*?

JoinedOrSeparate doesn't allow a trailing "=" right now. I think that
should be addressed in TableGen/libOption first.

> You might want to add a comment that if the directory for -L begins with =,
> it'll be replaced with sysroot directory.

That's essentially the interface contract. Same applies to other
options that are either in the "target" namespace or not.

> Probably you might want to define a function,
> maybeReplaceSysrootDirectory() or something, for this code pattern?

Will do once I add the next consumer?

Joerg