Created attachment 530180 [details] emerge --info Fail with gcc-7.3.0-r2 and gcc-8.1.0-r1.
Created attachment 530182 [details] build.log
Created attachment 530184 [details] autoconf-1.out
*** This bug has been marked as a duplicate of bug 654600 ***
Please change your portage version (probably upgrade). The version you have currently has a regression and that version isn't in main package tree anymore due to that even.