Created attachment 197249 [details]
USES=compiler:c++11-lang and USE_CXXSTD=c++11 are needed to fix build on architectures that use GCC as cc.
Tested on CURRENT with powerpc64 and amd64.
I've already tested the patch, it is in my commit queue.
A commit references this bug:
Date: Fri Sep 21 11:33:10 UTC 2018
New revision: 480257
Fix build on gcc-based archs.
Submitted by: Piotr Kubaj
Approved by: portmgr (tier-2 blanket)