[Issue 23631] [REG master] ./src/importc.h:80:8: warning: undefining "__has_builtin"

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23631

--- Comment #3 from Iain Buclaw <ibuclaw at gdcproject.org> ---
(In reply to Walter Bright from comment #2)
> ImportC does not has builtin, and those macros are predefined by cpp.
> Therefore, cpp is run with -Wno-builtin-macro-redefined.
> 
> Perhaps you are building with an earlier dmd? That -W switch was added to
> dmd's call to cpp very recently.

No, you are not seeing this because you're building with an outdated toolcahin.
I'm building master, everything is broken since
https://github.com/dlang/dmd/pull/14801

CI is also broken when updating to latest toolchain, so I've had to revert it
here: https://github.com/dlang/dmd/pull/14824

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