Adding a cast to the assignment to remove the "const", as above (or better yet, removing the "const" from the declaration of inlet_outlet), is really the correct fix - the #pragma based approach just tells the compiler to ignore the issue. You could keep a copy of the file with the fix outside the Axoloti library folder tree and copy it over the updated file back after each update, at least until a proper fix is done upstream. Kind of a pain, and you really should check to make sure the only difference between the file you are copying and the one you are replacing is the change you made to avoid missing actual upstream fixes, but it would be a bit easier than re-editing the file each time...
My $0.02 (Canadian),
John