`strftime` uses `__cdecl` and not `__stdcall`. This was exposed by
refactoring in commit 26c9fbab (MINGW-w64: Fix string(TIMESTAMP) build
on 32bits, 2021-11-16, v3.22.0~1^2).
This fixes a crash creating a timestamp with clang+mingw-w64 targeting x86.
39 jobs for !6762 with fix-mingw-strftime-crash in 5 minutes and 10 seconds
(queued for 1 second)