[Issue 13517] Only touch .di generated file if changed

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13517

--- Comment #21 from Andrei Alexandrescu <andrei at erdani.com> ---
(In reply to Steven Schveighoffer from comment #18)
> I would add a stipulation that if the purpose of the compiler invocation is
> ONLY to build the .di file, then the compiler should rewrite it. So dmd -c
> -o- -H should still touch the .di file even if it's identical to the
> existing one.
> 
> Otherwise, this disfavors a build system where the .di is built as a
> separate step (and causes a continual "rebuild" of a .di file every time the
> build is called).

Wouldn't that be easily achieved by "rm -rf generated/*.di" at the beginning of
that separate step?

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