Bug#854368: gcc-mingw-w64: programs built with --coverage do not create *.gcda files

[Giulio Paci]

I confirm the bug with gcc-mingw-w64-i686 version 6.3.0-18+19.3+b3 as well.

Upstream has recently closed the bug as non-reproducible:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79392