package/dhrystone: fix builds with GCC 15
GCC 15 defaults to -std=gnu23, which handles function declarations without
parameters differently from earlier C standards leading to compilation
errors:
dhry_1.c: In function ‘main’:
dhry_1.c:176:19: error: too many arguments to function ‘Func_2’; expected 0, have 2
176 | Bool_Glob = ! Func_2 (Str_1_Loc, Str_2_Loc);
https://gcc.gnu.org/gcc-15/porting_to.html#c23-fn-decls-without-parameters
As a workaround, force the build to use -std=gnu99 mode.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>
Peter Korsgaard