Investigate using Fortitude: Fortran linter

[danielhollas]

Fortitude is a (very) new Fortran linter inspired by the Python linter Ruff (and actually using some of its code!).

https://fortran-lang.discourse.group/t/fortitude-a-fortran-linter/8834

It's still very early but just quickly playing with it already proved useful.

Ultimately it would be nice to have it run automatically in CI, once they improve the configuration a bit (for example we need to ignore some of the files)

[danielhollas]

Whoops 😅

fortitude: 43 files scanned.
Number of errors: 1286

EDIT: Things are not that bad, most of the errors come from a single file

❯ fortitude check src/fftw3.F90 | tail
fortitude: 1 files scanned.
Number of errors: 861