Log Message:
lang/gcc5-aux: Fix runpath, at least for non-NetBSD platforms

NetBSD doesn't seem to be honoring -rpath, at least not with binutils
from base.  Using binutils from pkgsrc doesn't work either because it
uses the gold linker (for an unknown reason) which fails with an
"unsupported operation".  As a result, gcc5-aux was limited to base
binutils for NetBSD 7 and later.  The issue was never resolved.