With link-time optimization turned on, the function might be dropped
if it is not exported, because it's not used anywhere. This is what
happens for me with Clang 9.
If the function is dropped, -Wl,-fini=__kmp_internal_end_fini doesn't
do what we want: with ld.bfd and lld it drops the FINI attribute from
.dynamic and with gold we get FINI = 0x0, which leads to a crash on
cleanup. This can be reproduced by building with
and then running `readelf -d libomp.so`.