devel/kore: fix build on armv7 and clean up
- fix a warning about a wrong formatting specifier
- exorcise -Werror so future warnings do not break the build
- as a result, simplify Makefile
- switch to C11 to avoid some warnings
- reinstate %%OPENSSLINC%% patch bits dropped in previous commit
- patch in %%LOCALBASE%% correctly
MFH: 2023Q4
(cherry picked from commit bd7b56ae1896ca6c74df5ae31fee35efd107caa7)