Created attachment 180783 [details] failed build log from poudriere. as there is USES= compiler:c++11-lib in Makefile, CXX="g++49" is specified on MAKE_ENV section, but at the build phase, "g++" is used as the command. On powerpc64, it triggers gcc 4.2.1 in base, which does not support c++11. poudriere log on FreeBSD/powerpc64 r313561 attached.
This is basically a dup of PR204923 .. g++49 is used to recognize whether it's clang or gcc, and then the mkspec file for g++ is used. And *that* file sets the compiler to g++, no suffix, regardless of the environment. Loise mentions in the other PR she's working on this upstream, but it's slow going.
*** This bug has been marked as a duplicate of bug 204923 ***