[PATCH] sim: tests: support .S files

[DJ Delorie]

> > Rather than requiring all sim tests to be preprocessed .s files, add
> > support for .S files so we can easily write code using normal CPP
> > defines/macros.
> 
> not that I actually care about any such targets, but wouldn't this
> just fall over on a case insentive filesystem?

It works if you use explicit rules to find the .S files, or have
pattern rules for .S but not .s with an explicit list of targets.
It's when you rely on wildcards to scan for *.[sS] files that things
go badly.