Fixes #15434: object.d must not import from rt

[yazd]

https://issues.dlang.org/show_bug.cgi?id=15434

[yazd]

The auto-tester fails for some reason.. uhmm. I cannot reproduce the failure on either a 32-bit or a 64-bit linux.

[schveiguy]

Seems it was a spurious failure, passed now.

[schveiguy]

I've not seen externDFunc before, interesting! Is that really the only way to declare an external d function? Almost all other runtime extern functions are hooked via C linkage. I'm not sure which way is better.

[yazd]

It is used several times in this file to link to rt functions.

[schveiguy]

OK, then I guess I just haven't read through it in a while :)
LGTM

[PetarKirov]

@yazd thanks for fixing this!

Btw I wonder how it worked in debug (no inline) mode.

@schveiguy this is a regression from DMD 2.067 (when the code used to work), so I hope this PR will be merged in time for the next release.

[yazd]

@ZombineDev 👍
I think it works with no inline because the compiler only uses the declaration and links directly to the compiled druntime (it doesn't recompile druntime). I might be wrong.

Is there anything else to address to get this pulled?
Thanks.