[Issue 18145] Phobos makefile incorrectly sets --dip1000 for DMD when BUILD=debug

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18145

--- Comment #2 from Seb <greensunny12 at gmail.com> ---
(For reference, I can't reproduce this on Linux with Make 4.2.1)

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