The issue is that compilation is done with `x86_64-w64-mingw32-g++-posix`,
but then linking is done with `x86_64-w64-mingw32-g++`.
I'm guessing this has been broken since #24131
(01d1845a80ae48d741deea695ddce95d940ab0d8), but have not checked.
Fixes#29734.
Unblocks #29527 (now DEBUG=1 builds can be tested).
Github-Pull: #29747
Rebased-From: b7e7e727abd86104ee58beb648a94e2f453d1f6d