devel/kore: Fix build on powerpc/powerpc64

For some reason index(3) is not hidden when building with gcc 4.2.
Use a newer compiler to work around this.

src/config.c: In function 'configure_filemap_index':
src/config.c:812: warning: declaration of 'index' shadows a global declaration
/usr/include/strings.h:62: warning: shadowed declaration is here

PR: 235979
Reported by: pkubaj@anongoth.pl