https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69310
--- Comment #10 from Jack Howarth <howarth.at.gcc at gmail dot com> --- It is unclear if the changes in r232454, to avoid the explicit linkage on libitm, can ever be made darwin-friendly. On darwin, every single executable linked against libstdc++ would require -Wl,-undefined,dynamic_lookup on the linkage to avoid linkage errors from the undefined symbols from libitm within libstdc++.
