It has been suggested that we need (synchronous) unwind tables on POWER. The elfutils testsuite fails without them. In general, we get them for most packages because we compile with -fexceptions. But some parts of glibc are compiled without that, and they do not receive any unwind tables at all. POWER doesn't need asynchronous unwind tables, but I suggest to patch gcc (like we do for aarch64) so that it generates, by default, the unwind tables our tools expected.
I have put a redhat-rpm-config workaround into rawhide (f28 will follow), but the GCC defaults really should align with the flags in redhat-rpm-config in this area IMHO.
This seems to work fine for both rawhide and f28, but it looks like we also need it in f27.
Upstream has: 2018-04-10 Segher Boessenkool <segher.org> * common/config/rs6000/rs6000-common.c (rs6000_option_init_struct): Enable -fasynchronous-unwind-tables by default if OBJECT_FORMAT_ELF. I'm not sure which Fedora package release contains the change, but it's been committed upstream before the GCC 8 branch was created, so Fedora 28 and rawhide will eventually receive this change. I will update redhat-rpm-config accordingly.