gnucash @5.3: error: no member named 'merge' in 'std::__1::map

[ryandesign (Ryan Carsten Schmidt)]

​gnucash 5.3 fails to build on Mojave:

gnucash/import-export/csv-imp/gnc-import-tx.cpp:904:20: error: no member named 'merge' in 'std::__1::map<GncTransPropType, std::__1::basic_string<char>, std::__1::less<GncTransPropType>, std::__1::allocator<std::__1::pair<const GncTransPropType, std::__1::basic_string<char> > > >'
        all_errors.merge (split_props->errors());
        ~~~~~~~~~~ ^

It ​sounds like Apple clang didn't support merge until recently while llvm.org's clang does, so those older Apple clangs should be excluded with:

PortGroup compiler_blacklist_versions 1.0

compiler.blacklist-append {clang < 1100}

On High Sierra and earlier, it fails with a different error; see #67545.