`testrunner` asserts on MSYS MINGW64

[firewave]

Encountered while working on #475.

C:/msys64/mingw64/include/c++/15.1.0/bits/basic_string.h:1349: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::const_reference std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator[](size_type) const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; const_reference = const char&; size_type = long long unsigned int]: Assertion '__pos <= size()' failed.

I can reproduce it locally but for some reason the assertion does not break into the debugger so I have no trace. And I cannot reproduce it in a non-MSYS2 MinGW.

[firewave]

It happens in the timeDefine test.

That also fails several testing asserts:

------ assertion failed ---------
line 2891
expected:10
actual:2
------ assertion failed ---------
line 2894
expected:1
actual:0
------ assertion failed ---------
line 2895
expected:1
actual:0

[firewave]

The problem is that the asserts do not bail out.

The underlying issue is actually #391.