Created attachment 200819 [details]
This port doesn't build after default GCC version in ports was changed to 8.
Use older GCC (5) to build this port. GCC 7 could also be used, but GCC 5 is installed anyway on most GCC architectures, because it's needed for GCC 8.
Remove USES=compiler:c++11-lib, leave only USES=compiler. The reason is that compiler:c++11-lib overwrites USE_GCC and makes the port use GCC 8.
Tested on powerpc64 and amd64.
Hardware sponsored by IntegriCloud.
A commit references this bug:
Date: Thu Jan 17 23:29:32 UTC 2019
New revision: 490610
More throughly disable assertions. This works around USES=cmake
overriding the CFLAGS used to build. 
devel/llvm0: Fix build on GCC systems. 
devel/llvm: Avoid realpath calls where possible in the wrapper
PR: 233506 , 234647 , 234937 
Submitted by: email@example.com , firstname.lastname@example.org ,
Differential Revision: https://reviews.freebsd.org/D17990
Thanks for the submission.