"g++6"    -o "bin.v2/libs/stacktrace/build/gcc-6.4.0/debug/addr2line_exe" -Wl,--start-group "bin.v2/libs/stacktrace/build/gcc-6.4.0/debug/has_addr2line.o"  -Wl,-Bstatic  -Wl,-Bdynamic  -Wl,--end-group -g -m64
/usr/lib/libstdc++.so.6: version GLIBCXX_3.4.21 required by /wrkdirs/usr/ports/devel/boost-libs/work/boost_1_65_1/bin.v2/libs/stacktrace/build/gcc-6.4.0/debug/addr2line_exe not found
[...]
Error: Missing: lib/libboost_stacktrace_addr2line.a
Error: Missing: lib/libboost_stacktrace_addr2line.so
Error: Missing: lib/libboost_stacktrace_addr2line.so.%%BOOST_SHARED_LIB_VER%%