ltp: Fix build on x86/musl

ltp: Fix build on x86/musl

In last patch it covered out the non-glibc case well
but did not define else case, when __GLIBC__ is not
defined, as a result errors like

| getcpu01.c:107:41: error: use of undeclared identifier 'sys_support'
|         if (((tst_kvercmp(2, 6, 20)) < 0) || !(sys_support)) {

appeared, fixed it with this updated patch

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>