This should likely be re-factored out of busybox, as I believe kernel24 is now obsolete. (The problem was discovered on a configuration where MACHINE_FEATURES was not set.)
Busybox checks if MACHINE_FEATURES contains "kernel24". If so, CONFIG_FEATURE_2_4_MODULES will be on "y". kernel24 is no longer present in any machines configuration so yes, indeed it is obsolete. busybox_cfg('kernel24', machine_features, 'CONFIG_FEATURE_2_4_MODULES', cnf, rem) The same situation is in uglibc: uclibc_cfg('kernel24', machine_features,'UCLIBC_LINUX_MODULE_24', cnf, rem) This bug would be solved by removing these two lines.
http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=e2a3695ad44935e8dba6fb4d6e631fc7af5ab754