CONFIG_S390_MODULES_SANITY_TEST is not available for thedefaultarchitecture x86.
Result is shown for architecture s390

Enable s390 specific modules tests

modulename: test_modules.ko

configname: CONFIG_S390_MODULES_SANITY_TEST

Linux Kernel Configuration
└─>Selftests
└─>Enable s390 specific modules tests
In linux kernel since version 5.2 (release Date: 2019-07-07)  
This option enables an s390 specific modules test. This option is
not useful for distributions or general kernels, but only for
kernel developers working on architecture code.

Say N if you are unsure.

source code: