Please, include USE_GCC=5.0 option in common macros. Thank you in advance.
Yes, it fails because we have not added it, and I have to admit I am bit sceptical about the benefit of this for the time being since GCC 5 is under very active development still and far from stabilization. (Just last week it failed to build for me about half thhe time.) Still, since you are interested I'll be add support for USE_GCC=5 (not USE_GCC=5.0 since the version scheme of GCC is changing.)
A commit references this bug: Author: gerald Date: Sun Nov 2 21:15:21 UTC 2014 New revision: 372091 URL: https://svnweb.freebsd.org/changeset/ports/372091 Log: Add support for USE_GCC=5 and its preferred form USE_GCC=5+. PR: 194676 Changes: head/Mk/bsd.gcc.mk