https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85915
--- Comment #11 from Luke Dashjr <luke-jr+gccbugs at utopios dot org> --- Simply upgrading to GCC 8.2.0 failed due to the multiple-definition of __x86_return_thunk, so I successfully built only the C compiler with the non-thunking defaults; from there, I rebuilt glibc again without thunking, then rebuilt the full GCC with thunking re-enabled, and glibc again with thunking re-enabled. My most recent issue was with building distcc and libiberty.a, which I solved by removing binutils-libs and installing it again from scratch (a simple rebuild failed due to the multiple-definition of __x86_return_thunk in the existing library).
