I ran cmake with "VERBOSE=1", and you do use the -Wall setting, but
you can get even more warnings with -Wextra and -pedantic. There's more
as well:
https://kristerw.blogspot.com/2017/09/useful-gcc-warning-options-not-enabled.html
By the way, I see a metric ton of -D defines on the command line, including
the misspelled "-DPOLIPHONY=80". A header file would be a better place for
those, IMHO.
Anyway, onward and upward!
-------- Will Godfrey 13:35 Thu 26 Oct --------
Yes, these seem quite reasonable. It would seem your compiler is more fussy
than gcc!