[Bug c++/103118] [modules] ICE tree check in get_merge_kind at cp/module.cc

[johelegp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103118

--- Comment #3 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
What works is including them in a non-module unit translation unit.

```C++
#if defined(__GNUC__) and not defined(__clang__)
#  include <chrono> // Workaround GCC bug 103118.
#  include <span>   // Workaround GCC bug 100583.
#endif
import waarudo.geometries;
import waarudo.numbers;
import waarudo.quantities;
#include <cassert>
```