Created attachment 52266 [details]
ii files for errors

Build fails with the following:

ld: duplicate symbol icu_67::number::NumberFormatterSettings<icu_67::number::UnlocalizedNumberFormatter>::copyErrorTo(UErrorCode&) const in number_skeletons.o and number_fluent.o
collect2: error: ld returned 1 exit status
make[1]: *** [../lib/libicui18n.67.1.dylib] Error 1
make: *** [all-recursive] Error 2

Commands producing the faulty objects:

/opt/local/bin/g++-mp-6 -m64 -O2 -DU_ATTRIBUTE_DEPRECATED= -DU_I18N_IMPLEMENTATION -DU_HAVE_STRTOD_L=1 -DU_HAVE_XLOCALE_H=1 -I. -I../common -O2 -W -Wall -pedantic -Wpointer-arith -Wwrite-strings -Wno-long-long -std=c++11 -fvisibility=hidden -fno-common -c -dynamic -MMD -MT "number_skeletons.d number_skeletons.o number_skeletons.ao" -o number_skeletons.o number_skeletons.cpp

/opt/local/bin/g++-mp-6 -m64 -O2 -DU_ATTRIBUTE_DEPRECATED= -DU_I18N_IMPLEMENTATION -DU_HAVE_STRTOD_L=1 -DU_HAVE_XLOCALE_H=1 -I. -I../common -O2 -W -Wall -pedantic -Wpointer-arith -Wwrite-strings -Wno-long-long -std=c++11 -fvisibility=hidden -fno-common -c -dynamic -MMD -MT "number_fluent.d number_fluent.o number_fluent.ao" -o number_fluent.o number_fluent.cpp

P. S. Error unrelated to Macports, I have redone the build outside with cleared path, and it fails identically. ii files in attachment are from the build outside of Macports.